Invesco Stable Asset Trust

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Invesco National Trust Company

Annual Report

Year Ended December 31, 2013

Invesco Stable Asset Trust

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01 Schedule of Portfolio Investments

03 Statement of Assets and Liabilities

04 Statement of Operations

05 Statement of Changes in Net Assets

06 Financial Highlights

07 Schedule of Securities Purchased, Sold or Matured

08 Notes to Financial Statements

15 Report of Independent Auditors

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Schedule of Portfolio Investments December 31, 2013

Holdings ^ContractNumber

Wrap Provider

Credit

Rating(a) Yield(b) Units Cost Investments at Value

Wrap Contracts at

Value(c) Adjustment to

Contract Value Contract Value SYNTHETIC GUARANTEED INVESTMENT CONTRACTS (94.7%)

Invesco Group Trust for Retirement Savings American General Life Insurance 1642144 A+

Invesco Short Duration Fund^ 0.89% 132,646,421 $132,647,035 $132,130,824 $ — $(857,705) $131,273,119 Invesco Core Fixed Income Fund^ 2.40% 14,428,587 23,408,636 23,303,366 — (151,270) 23,152,096

Massachusetts Mutual 20039 AA+

Massachusetts Mutual Babson 1-5

Year Government/Credit* 1.36% 155,362,324 192,187,871 155,362,324 — (2,203,232) 153,159,092 Massachusetts Mutual Babson

SA Intermediate Government/

Credit* 1.91% 51,664,804 50,674,503 51,664,804 — (732,672) 50,932,132

Metropolitan Life GAC 32494 AA-

Metropolitan Life PIMCO 1-3

Year Government/Credit* 1.15% 85,908,535 145,024,752 85,908,535 — (103,001) 85,805,534 Metropolitan Life BlackRock

Intermediate Government/

Credit* 1.40% 57,791,235 58,049,901 57,791,235 — (69,289) 57,721,946

Monumental MDA-01235TR AA-

Invesco Short-Term Bond Fund^ 1.11% 61,233,366 96,647,806 96,492,029 — (1,275,594) 95,216,435 Invesco Intermediate

Government/Credit Fund^ 1.76% 8,963,796 17,055,495 17,021,639 — (225,021) 16,796,618

New York Life GA-29005 AA+

New York Life 1 - 5 Year

Government/Credit* 0.95% 100,000,000 100,000,000 104,697,365 — (1,172,980) 103,524,385 Prudential Insurance Co. GA-62328 AA-

Invesco Short-Term Bond Fund^ 1.11% 29,295,648 46,175,274 46,164,317 — (639,461) 45,524,856 Jennison 1-5 Year

Government/Credit Fund^ 1.08% 43,713,607 46,175,251 45,778,900 — (634,122) 45,144,778 Invesco Intermediate

Government/Credit Fund^ 1.76% 12,128,590 23,087,644 23,031,368 — (319,027) 22,712,341 Jennison Intermediate

Government/Credit Fund^ 1.51% 38,558,646 69,262,896 68,584,264 — (950,019) 67,634,245 Invesco Core Fixed Income Fund^ 2.40% 7,058,681 11,543,823 11,400,355 — (157,916) 11,242,439 Invesco PIMCO Intermediate

Government/Credit Fund^ 1.48% 9,622,256 23,087,642 22,780,692 — (315,555) 22,465,137 Invesco PIMCO Core Fixed

Income Fund^ 2.07% 6,687,419 11,543,823 11,297,725 — (156,494) 11,141,231

TOTAL SYNTHETIC GUARANTEED

INVESTMENT CONTRACTS $1,046,572,352 $953,409,742 $— $(9,963,358) $943,446,384

SHORT-TERM INVESTMENT (6.6%)

Invesco Short-Term Investment Fund^ 65,325,752 $65,325,752 $65,325,752 $— $— $65,325,752

TOTAL SHORT-TERM INVESTMENT $65,325,752 $65,325,752 $— $— $65,325,752

TOTAL INVESTMENTS $1,111,898,104 $1,018,735,494 $— $(9,963,358) $1,008,772,136

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2 Invesco Stable Asset Trust

Schedule of Portfolio Investments December 31, 2013

See notes to financial statements.

The following is a summary of the inputs used to value the Trust’s Investments and Financial Instruments as of December 31, 2013:

Trust LEVEL 1 LEVEL 2 LEVEL 3 Total

Affiliated Collective Trusts $— $497,985,479 $— $497,985,479

Insurance Company Separate Accounts — 455,424,263 — 455,424,263

Short-Term Investment 65,325,752 — — 65,325,752

Total Investments $65,325,752 $953,409,742 $— $1,018,735,494

^ The security and the Trust are advised by wholly-owned subsidiaries of Invesco, Ltd., and are therefore considered to be affiliated. See Footnote 4.

* Insurance Company Separate Accounts.

(a) Represents published Standard & Poor’s ratings as of December 31, 2013. (b) Represents the yield of the underlying holdings.

(c) Issuer ratings are used as inputs to the fair value calculation for wrap contracts. The issuer ratings used for the purpose of these calculations were determined by converting the highest of the three published ratings from Standard & Poor’s, Moody’s and Fitch as of December 31, 2013, to the equivalent Standard & Poor’s rating. See Footnote 2 for further discussion of inputs.

The Portfolio is comprised of 6 individual wrap contracts which are issued by separate issuers and 16 underlying holding positions. The contract value by issuer is as follows:

Percentage of Contract Value

Prudential Insurance Co. 23.9%

Massachusetts Mutual 21.6%

American General Life Insurance Co. 16.4%

Metropolitan Life 15.2%

Monumental 11.9%

New York Life 11.0%

100.0%

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Statement of Assets and Liabilities December 31, 2013

Assets: Investments:

Investments in affiliated securities, at value (cost $565,961,077) $ 563,311,231

Investments in unaffiliated securities, at value (cost $545,937,027) 455,424,263

Total investments at value (Note 5) 1,018,735,494

Interest and dividends receivable 10,541

Receivable from units issued 842,336

Total Assets 1,019,588,371

Liabilities:

Payable for units redeemed 12,937,131

Management fees payable 718,938

Other accrued expenses 9,809

Total Liabilities 13,665,878

Net Assets (at value) 1,005,922,493

Adjustment from Value to Contract Value (Note 5) (9,963,358)

Net Assets (at contract value) (Note 5) 995,959,135

ADP85 Units:

Net Assets (at contract value) $ 778,660,294

Units Outstanding 778,660,294

Net Unit Value (at contract value) $ 1.00

ADP30 Units:

ADP59 Units:

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Statement of Operations

For the Year Ended December 31, 2013

See notes to financial statements. Investment Income:

Credit rate income on wrap contracts $ 16,858,475

Income from affiliated securities 121,969

Total Investment Income 16,980,444

Wrap fees (2,378,949)

Investment income after wrap fees 14,601,495

Expenses:

Accounting fees 30,780

Professional fees 23,268

Custodian fees 1,858

Transfer agent fees 14,730

Management fees - ADP85 6,869,115

Management fees - ADP30 499,085

Management fees - ADP59 133,870

Net Expenses 7,572,706

Net Investment Income $ 7,028,789

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Statement of Changes in Net Assets For the Year Ended December 31, 2013

Net Assets, Beginning of Year $ 993,822,461

Operations:

Net investment income 7,028,789

Change in net assets resulting from operations 7,028,789

Distributions to ADP30 Unitholders:

From net investment income (1,917,721)

From net investment income (182,287)

From net investment income (4,928,781)

Change in net assets from Distributions to unitholders (7,028,789)

Capital Transactions to ADP30 Unitholders

Proceeds from units issued 51,284,924

Distributions reinvested 1,917,725

Cost of units redeemed (30,456,302)

Change in net assets from ADP30 Units 22,746,347

Distributions reinvested 182,287

Change in net assets from ADP59 Units 33,825,644

Distributions reinvested 4,928,774

Change in net assets from ADP85 Units (54,435,317)

Change in net assets resulting from capital transactions 2,136,674

Change in net assets 2,136,674

Net Assets, End of Year $ 995,959,135

Unit Transactions to ADP85 Unitholders

Issued 148,844,326

Reinvested 4,928,774

Redeemed (208,208,418)

Change in ADP85 Units (54,435,318)

Issued 51,284,924

Reinvested 1,917,725

Redeemed (30,456,302)

Change in ADP30 Units 22,746,347

Issued 38,460,742

Reinvested 182,287

Redeemed (4,817,385)

Change in ADP59 Units 33,825,644

Total Change in Units 2,136,674

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Financial Highlights

For the Year Ended December 31, 2013

See notes to financial statements. Per Unit Operating Performance

(for a unit outstanding throughout the year) :

Change in Net Unit Value Less Ratios

Resulting from Operations: Distributions from: (to average net assets): Net Unit

Value, Beginning of

Year

Net Investment Income (a)

Total from Investment Activities

Net Investment

Income Distributions^Total

Net Unit Value, End of

Year Return^Total Expenses^Net

Net Investment

Income

ADP85 Units

Year Ended December 31, 2013 $1.00 0.01 0.01 (0.01) (0.01) $1.00 0.61% 0.86% 0.61%

ADP30 Units

ADP59 Units

(a) Per unit amounts are based on average daily units outstanding.

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Schedule of Securities Purchased, Sold, or Matured For the Year Ended December 31, 2013

Cost of Shares or Principal Amount Purchased:

Affiliated Collective Trusts . . . $ 265,595,427 Insurance Company Separate Accounts . . . — Short-Term Investment . . . 197,255,732

$ 462,851,159 Cost of Shares or Principal Amount Sold/Matured:

Affiliated Collective Trusts . . . $ 295,642,241 Insurance Company Separate Accounts . . . — Short-Term Investment . . . 162,430,081

$ 458,072,322 Sales/Maturity Proceeds

Affiliated Collective Trusts . . . $ (295,642,241) Insurance Company Separate Accounts . . . — Short-Term Investment . . . (162,430,081)

$ (458,072,322)

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Notes to Financial Statements December 31, 2013

NOTE 1 - ORGANIZATION AND DESCRIPTION OF THE TRUSTS

Invesco Stable Asset Trust (the “Trust”) is a collective trust established by Invesco National Trust Company, a national trust bank organized and existing under the laws of the United States (the “Trustee” or the “Company”), effective as of January 21, 2011. This collective Trust was established for purposes of collectively investing and reinvesting the assets of eligible pension and profit sharing trusts and other eligible entities. The Trust’s primary investment objectives are to seek the preservation of principal and to provide interest income reasonably obtained under prevailing market conditions and rates, consistent with seeking to maintain required liquidity.

NOTE 2 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

In accordance with Accounting Standards Codification (“ASC”) 946-210-45 through 946-210-55, Reporting of Fully Benefit-Responsive Investment Contracts, investments held by the Trust are required to be reported at fair value, which is generally determined as the amount that could reasonably be expected to realize from an orderly disposition of securities and other financial instruments over a reasonable period of time. However, contract value is the relevant measurement attribute for that portion of the net assets of the Trust attributable to fully benefit responsive investment contracts because contract value is the amount unitholders would receive if they were to initiate permitted transactions under the terms of the underlying defined contribution plans. The accompanying Schedule of Portfolio Investments reflects both the fair value as well as the adjustment to contract value for each investment contract deemed fully benefit-responsive. The Statement of Assets and Liabilities presents the fair value of the investment contracts as well as the adjustment of the fully benefit-responsive investment contracts from fair value to contract value. The Statement of Operations and Statement of Changes in Net Assets was prepared on a contract value basis. A. Security Valuation

Securities are valued according to the following policy.

The Trust may invest in bank, insurance company and other financial institution investment contracts (“GICs”). The Trust holds synthetic guaranteed investment contracts (“synthetic GICs”). Synthetic GICs are portfolios of securities (debt securities or units of collective trusts) owned by the Trust with wrap contracts associated with the portfolios. The Trust’s investments contracts are carried at contract value which is equal to principal balance plus accrued interest plus deposits and less withdrawals. An investment contract is generally permitted to be valued at contract value, rather than fair value, to the extent it is fully benefit-responsive and held by a trust offered only to qualified employer- sponsored defined-contribution plans. Investment contracts that do not meet the criteria for valuation at contract value will be valued at fair value as determined by the Trustee, and such value may be more or less than contract value. Investment contracts have elements of risk due to lack of a secondary market and resale restrictions resulting in the inability of the Trust to sell a contract. In addition, investment contracts may be subject to credit risk based on the ability of the wrapper providers to meet their obligations under the terms of the contract (see Note 5). The Trust may also invest in traditional guaranteed investment contracts (“traditional GICs”). Traditional GICs are backed by the general account of the issuer. The Trust deposits a lump sum with the issuer and receives a guaranteed interest rate for a specified time. Interest is accrued on either a simple interest or fully compounded basis and paid either periodically or at the end of the contract term. The issuer guarantees that all qualified participant withdrawals, as defined, will occur at contract value (principal plus accrued interest). Traditional GICs generally do not permit issuers to terminate the agreement prior to the scheduled maturity date. The fair value of traditional GICs is determined using an income approach where the individual contract cash flows are discounted at the prevailing interpolated swap rate as of year-end.

Short-term securities are stated at amortized cost (which approximates market value) if maturity is 60 days or less at the time of purchase, or at market value if maturity is greater than 60 days.

Investments in units of affiliated collective trusts (see Note 4) are valued at the respective net asset values as reported by such Trusts. Debt obligations (including convertible bonds) and unlisted equities are fair valued using an evaluated quote provided by an independent pricing service. Evaluated quotes provided by the pricing service may be determined without exclusive reliance on quoted prices, and may reflect appropriate factors such as institution-size trading in similar groups of securities, developments related to specific securities, dividend rate (for unlisted equities), yield (for debt obligations), quality, type of issue, coupon rate (for debt obligations), maturity (for debt obligations), individual trading characteristics and other market data. Debt obligations are subject to interest rate and credit risks. In addition, all debt obligations involve some risk of default with respect to interest and/or principal payments.

The fair value of the separate account insurance contracts is based on the net asset value of an insurance company separate account on which the crediting rate is based. the underlying fixed income securities of the separate accounts are valued on the basis of valuation furnished by approved independent pricing services. These services determine valuations for normal institutional-size trading units of such securities using model or matrix pricing.

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Securities for which market prices are not provided by any of the above methods may be valued based upon quotes furnished by independent sources. The last bid price may be used to value equity securities. The last bid is used to value debt obligations, including corporate loans. Securities for which market quotations are not readily available or became unreliable are valued at fair value as determined in good faith by or under the supervision of the Trust’s officers following procedures approved by the Board of Trustees. Issuer specific events, market trends, bid/ask quotes of brokers and information providers and other market data may be reviewed in the course of making a good faith determination of a security’s fair value.

Valuations change in response to many factors including the historical and prospective earnings of the issuer, the value of the issuer’s assets, general economic conditions, interest rates, investor perceptions and market liquidity. Because of the inherent uncertainties of valuation, the values reflected in the financial statements may materially differ from the value received upon actual sale of those investments.

B. Investment Transactions and Investment Income

Investment transactions are accounted for on a trade date basis. Realized gains or losses on sales are computed on the basis of specific identification on the securities sold. Interest income, if any, is recorded on the accrual basis. Distributions from ordinary income from underlying funds, if any, are recorded as dividend income on ex-dividend date. Distributions from gains from underlying funds, if any, are recorded as realized gains on ex-dividend date. Income from investment contracts is recorded at the contract rate, which in the case of synthetic investment contracts is referred to as the crediting rate. Crediting rates on synthetic contracts are net of fees to the issuer of the wrap contract and custody fees on underlying assets. For fully benefit-responsive synthetic investment contracts, earnings on the underlying assets are factored in the next computation of the crediting rate re-set.

The Trusts allocate investment income, realized and unrealized capital gains and losses to a unit class, if applicable, based on the relative net assets of each unit class.

C. Federal Income Taxes

No provision for federal income taxes has been recorded since the Trust is exempt under Section 584(b) of the Internal Revenue Code. The Trust has analyzed its uncertain tax positions for all open tax years (generally the last three years) and has concluded that no provision for income tax is required in its financial statements.

D. Unit Classes and Expenses

The Trust has multiple unit classes which share expenses, investment income and gains and losses as applicable on a proportionate basis. The Company may charge reasonable expenses incurred in operating the Trust, to the extent not prohibited by applicable law in the state in which the Company maintains IRT. However, the Company shall absorb any expenses of establishing or reorganizing the Trust. Expenses incurred by the Company in the performance of its duties which are charged to the Trust, include but are not limited to fees for legal services, custody, portfolio accounting, transfer agency, annual report preparation, and auditing services rendered to the Company, and all other proper charges and disbursements of the Company in connection with the administration of the Trust. Trusts that invest exclusively in units of other Invesco-Affiliated Collective Funds (See Note 4), do not incur custodian fees.

Accounting, Professional, Custodian and Transfer Agent Fees

Expenses chargeable to the Trust include those relating to, without limitation, management fees and expenses of vehicles in which the Trust invests, portfolio accounting and performance monitoring, legal services, transfer agency, custody, annual report preparation and distribution, overdraft charges and compensation paid to agents for monitoring and evaluation of the quality of service provided and the reasonableness of fees charged by other independent outside service providers engaged on behalf of the Trust. Expenses shall be charged to the class of units in such equitable proportion as may be determined by the Trustee. Extraordinary transaction costs attributable to a Participating Trust’s contribution to or redemption from the Trust may be charged to such Participating Trust in accordance with applicable law. All taxes that may be levied upon or in respect of the Trust or liquidating account under existing or future laws shall be charged to the Trust or liquidating account with respect to which such taxes were levied or assessed.

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Management Fees

The management fees for each class of units shall equal the proportionate share (by reference to the net asset value of each class of units relative to the net asset value of the Trust) of the aggregate management fees of all classes of units calculated in accordance with the following fee schedule (using the net asset value of the Trust); provided, that the management fees of each class of units shall not be less than $100,000 (the “Minimum Management Fee”).

Management fees are charged by the Company based on the average daily net assets of that Class, as follows: Management Fee

Class Annual Rate

ADP85 0.85%

ADP30 0.30%

ADP59 0.59%

E. Unit Transactions

Issuances and redemptions of participant units are made on each business day (“Valuation Date”). As permitted under the Trust’s Declaration of Trust (“Trust Agreement”), participant units are issued and redeemed based upon the NAV per unit of the Trust, determined in accordance with the terms of the Trust Agreement, as of the Trust’s Valuation Date last preceding the date on which such order to contribute assets or withdraw assets is received.

F. Accounting Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of investment income and expenses during the reporting period including estimates and assumptions related to taxation. Actual results could differ from those estimates by a significant amount. In addition, the Trusts monitor for material events or transactions that may occur or become known after the period-end date and before the date the financial statements are released to print. G. Indemnifications

Under the Trust Agreement, the Company is indemnified against certain liabilities arising out of the performance of its duties to the Trust. Additionally, in the normal course of business, the Company as trustee for the Trust, enters into contracts with its vendors and others that contain a variety of indemnification clauses. Each Trust’s maximum exposure under these arrangements is unknown, as this would involve future claims that may be made against a Trust. The risk of material loss as a result of such indemnification claims is considered remote. H. Unit Valuation, Issues, Redemptions and Distributions

The net unit values of the classes of the Trust are determined as of the close of each business day. In accordance with the terms of the Trust Agreement, participant units are issued and redeemed only at the end of each day and at the net unit value at contract value, provided that redeeming participant plans comply with the required one-year notice provision. When the market value of units is less than their contract value, participant plans may also elect to withdraw units at their market value upon 10 days’ notice.

Distributions of net investment income are declared daily and paid monthly. Such distributions are reinvested at the month-end net unit value. I. Other Risks

The Trust maintains investment contracts issued by insurance companies, banks and other financial institutions as required by the Declaration of Trust. The issuing institution’s ability to meet its contractual obligations under the under the respective contracts may be affected by future economic and regulatory developments in the insurance and banking industries.

NOTE 3 – ADDITIONAL VALUATION INFORMATION

Fair value is defined as the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (an exit price), under current market conditions. The fair values of each Trust’s investments are determined in accordance with valuation policies established by the Trustee. Fair value may not represent the net amount that a Trust would have received had it sold an asset or the net amount that it would have paid had it transferred a liability.

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GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, under current market conditions. GAAP establishes a hierarchy that prioritizes the inputs to valuation methods, giving the highest priority to readily available unadjusted quoted prices in an active market for identical assets (Level 1) and the lowest priority to significant unobservable inputs (Level 3), generally when market prices are not readily available or are unreliable. Based on the valuation inputs, the securities or other investments are tiered into one of three levels. Changes in valuation methods may result in transfers in or out of an investment’s assigned level:

Level 1 – Prices are determined using quoted prices in an active market for identical assets.

Level 2 – Prices are determined using other significant observable inputs. Observable inputs are inputs that other market participants may use in pricing a security. These may include quoted prices for similar securities, interest rates, prepayment speeds, credit risk, yield curves, loss severities, default rates, discount rates, volatilities and others.

Level 3 – Prices are determined using significant unobservable inputs. In situations where quoted prices or observable inputs are unavailable (for example, when there is little or no market activity for an investment at the end of the period), unobservable inputs may be used. Unobservable inputs reflect the Trust’s own assumptions about the factors market participants would use in determining fair value of the securities or instruments and would be based on the best available information.

The estimated value of the Collective Trust Funds and Insurance Company Separate Accounts is net asset value, exclusive of the adjustment to contract value, and is considered Level 2. The use of net asset value as fair value is deemed appropriate as the Collective Trust Funds and Insurance Company Separate Accounts do not have finite lives, unfunded commitments relating to these types of investments, or significant restrictions on redemptions.

Investments in Collective Trust Funds previously classified as Level 1 in December 31, 2012 financial statements are classified as Level 2 in the December 31, 2013 financial statements in accordance with GAAP.

A summary of valuation inputs can be found on the schedule of Portfolio investments. NOTE 4 – TRANSACTIONS WITH AFFILIATES

Investment management services are provided to the Trust by the Company, an indirectly wholly-owned subsidiary of Invesco Ltd. The Company is compensated as described in Note 2D. The Company has employed, at its own expense, Invesco Fixed Income, a division of Invesco Advisers, Inc., as sub-adviser to the Trust. Invesco Advisers, Inc., is an indirectly wholly-owned subsidiary of Invesco Ltd. The Trust invests in units of collective trust funds within Invesco Group Trust for Retirement Savings (“IGT”), a collective trust managed by the Company. See the Schedule of Portfolio Investments for the IGT cost and trust name, the percent of net assets that the IGT Trust represents of the total net assets of the Trust, and the value of the investment in the IGT Trust as of December 31, 2013. Redemptions of units in the IGT Trusts may be made daily.

The majority of the IGT Trusts are sub-advised by Invesco Advisers, Inc. (“Invesco”), which is an affiliate of the Company. Invesco does not charge any investment management fees on the IGT Trusts it sub-advises. Certain of the IGT Trusts in which the Trust invests are sub- advised by unaffiliated sub- advisers. These sub-advisers are paid investment management fees from the IGT Trusts they sub-advise. In addition, all IGT Trusts pay operating expenses including, but not limited to, portfolio accounting, audit, legal services, transfer agency, custody and annual report preparation and distribution. Further information regarding the fees paid to the unaffiliated sub-advisers and operating expenses for the IGT Trust is available upon request.

The Trust also invests in units of the Invesco STIF, a short-term investment vehicle managed by the Company. See the Schedule of Portfolio Investments for the cost, the percent of net assets that the Invesco STIF represents of the total net assets of the Trust, and the value of the investment in the Invesco STIF as of December 31, 2013. Redemptions of units in the Invesco STIF may be made daily.

Concentration of Ownership

As of December 31, 2013, 80.1% of the Trust’s outstanding units were owned by 2 unitholders.

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If the market value of the covered assets is less than their book value, the wrapper agreements are assets of the Trust with a value equal to the difference which will generally result in future interest crediting rates that are lower than current market yields. Conversely, if the market value of the covered asset is more than their book value, this generally results in a deduction from market value to contract value and future crediting rates that are higher than current market yields. The book value of the wrapper agreement is equal to the purchase price of covered assets less the sale price of covered assets sold to cover share redemptions plus interest accrued at the crediting rate.

To accomplish the primary objectives outlined in Note 1, the Trust enters into wrapper contracts (also known as synthetic GICs). In a synthetic GIC structure, the underlying investments are owned by the Trust for plan participants. The Trust enters into wrapper contracts from high-quality insurance companies or banks that serve to substantially offset the price fluctuations in the underlying investments caused by movements in interest rates. Each wrapper contract obligates the wrapper provider to maintain the “contract value” of the underlying investments. The contract value is generally equal to the principal amounts invested in the underlying investments, plus interest accrued at a crediting rate established under the contract, less any adjustments for withdrawals (as specified in the wrapper contract). Under the terms of the wrapper contract, the realized and unrealized gains and losses on the underlying investments are, in effect, amortized over the duration of the underlying investments through adjustments to the future contract interest crediting rate (which is the rate earned by participants in the Trust for the underlying investments). The wrapper contract provides that the adjustments to the interest crediting rate will not result in a interest crediting rate that is less than zero. This minimizes the risk of loss with respect to principal and interest.

In general, if the contract value of the wrapper contract exceeds the market value of the underlying investments (including accrued interest), the wrapper provider becomes obligated to pay that difference to the Trust in the event that shareholder redemptions result in a total contract liquidation. In the event that there are partial shareholder redemptions that would otherwise cause the contract’s crediting rate to fall below zero percent, the wrapper provider is obligated to contribute to the Trust an amount necessary to maintain the contract’s crediting rate of at least zero percent. The circumstance under which payments are made and the timing of payments between the Trust and the wrapper provider may vary based on the terms of the wrapper contract.

Calculating the Interest Crediting Rate in Wrapper Contracts

The key factors that influence future interest crediting rates for a wrapper contract include:

• The level of market interest rates

• The amount and timing of participant contributions, transfers, and withdrawals into/out of the wrapper contract

• The investment returns generated by the fixed income investments that back the wrapper contract

• The duration of the underlying fixed income investments backing the wrapper contract

Wrapper contracts’ interest crediting rates are typically reset on a monthly or quarterly basis according to each contract. While there may be slight variations from one contract to another, most wrapper contracts use a formula that is based on the characteristics of the underlying fixed income portfolio:

CR =[(1+YTM) x (MV/CV)1/Dur -1] – F Where: CR = Contract interest crediting rate

YTM = Yield to maturity of underlying investments MV = Market value of underlying investments

CV = Contract value (principal plus accrued crediting rate interest) Dur = Duration of the underlying investments

F = Wrapper contract fees

Over time, the crediting rate formula amortizes the Trust’s realized and unrealized market value gains and losses over the duration of the underlying investments.

Because changes in market interest rates affect the yield to maturity and the market value of the underlying investments, they can have a material impact on the wrapper contract’s interest crediting rate. In addition, participant withdrawals and transfers from the Trust are paid at contract value but funded through the market value liquidation of the underlying investments, which also impacts the interest crediting rate. The resulting difference between the market value of the underlying investments relative to the wrapper contract value is presented on the Trust’s Schedule of Portfolio Investments and Statement of Assets and Liabilities as the “Adjustment from Fair Value to Contract Value”. If the Adjustment from Fair Value to Contract Value is positive for a given contract, this indicates that the wrapper contract value is greater than the market value of the underlying investments. The embedded market value losses will be amortized in the future through a lower interest crediting rate. If the Adjustment from Fair Value to Contract Value is negative, this indicates that the wrapper contract value is less than the market value of the underlying investments. The amortization of the embedded market value gains will cause the future interest crediting rate to be higher.

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Events That Limit the Ability of the Trust to Transact at Contract Value

Investment contracts are valued at contract value principally because unitholders are able to transact at contract value when initiating benefit-responsive withdrawals, taking loans or making investment option transfers permitted by the participating plan. A benefit-responsive withdrawal includes a payment to a unitholder arising from retirement, termination of employment, disability or death. In the normal course, unitholder events are predictable (for unitholders as a group) such that the economic integrity of investment contracts is largely unaffected by unitholder withdrawals.

Employer initiated events, if material, may affect the underlying economics of investment contracts. These events include plant closings, layoffs, plan termination, bankruptcy or reorganization, merger, early retirement incentive programs, tax disqualification of a trust or other events. The occurrence of one or more employer initiated events could limit the Fund’s ability to transact at contract value with plan unitholders.

For example, retirement benefit payments which occur because an employer has offered a subsidized early retirement program will not transact at contract value unless the scope of the program is not material or the investment contract includes a “contract value corridor”. Whether an employer initiated event is probable is foremost within the knowledge of the employer, but in the normal course may be communicated to the investment manager of the Fund. While the investment manager may take action to minimize or eliminate the impact of the employer initiated event, there is no assurance that the issuer will continue to transact at contract value once the corridor is used. In that case, the Fund would be unable to maintain the ability to transact at contract value. As of December 31, 2013, Trust’s management believes the occurrence of an event that would limit the ability of the Fund to transact at contract value with the unitholders in the Fund is not probable.

Issuer-Initiated Contract Termination

Examples of events that would permit a wrapper contract issuer to terminate a wrapper contract upon short notice include the plan’s loss of its qualified status, material breaches of responsibilities that are not cured, or material and adverse changes to the provisions of the plan. If one of these events was to occur, the wrapper contract issuer could terminate the wrapper contract at the market value of the underlying investments (or in the case of a traditional GIC, at the hypothetical market value based upon a contractual formula).

Addendum to the December 31, 2013 Statement of Assets and Liabilities

Adjustment from value to contract value at 12/31/2012 $ (33,008,705)

Change in the difference between value and contract value of all fully benefit-responsive investment contracts 23,045,347

Change in the fully benefit-responsive status of the investment contracts —

Adjustment from value to contract value at 12/31/2013: $ (9,963,358)

Ratio of year end market value yield to investments (at value) 1.219%

Ratio of year end crediting rate to investments (at value) 1.300%

Ratio of year end market value to book value 100.99%

(17)

Addendum to the December 31, 2013 Statement of Assets and Liabilities (continued)

The following tables are presented to show the impact hypothetical changes in market interest rates would have on the crediting interest rates for synthetic GICs assuming constant duration of the underlying investments.

Average Portfolio Duration: 2.70 years Average Portfolio Crediting Rate: 1.31%

Market Interest Rate: 1.15%

Participant Cash Flows: 0.0%

Market Rate Shock: -50% -25% No change 25% 50%

Market Rate Scenario: 0.58% 0.86% 1.15 % 1.44% 1.73%

Immediate: December 31, 2014 1.31% 1.31% 1.31% 1.31% 1.31%

Period End: Q1 March 31, 2014 1.25% 1.27% 1.30% 1.32% 1.35%

Q2 June 30, 2014 1.18% 1.23% 1.28% 1.34% 1.39%

Q3 September 30, 2014 1.11% 1.19% 1.27% 1.35% 1.43%

Q4 December 31, 2014 1.04% 1.15% 1.25% 1.36% 1.47%

Participant Cash Flows: -10.0%

Market Rate Shock: -50% -25% No change 25% 50%

Market Rate Scenario: 0.58% 0.86% 1.15% 1.44% 1.73%

Immediate: December 31, 2013 1.31% 1.31% 1.31% 1.31% 1.31%

Period End: Q1 March 31, 2014 1.25% 1.28% 1.30% 1.32% 1.35%

Q2 June 30, 2014 1.19% 1.24% 1.29% 1.33% 1.38%

Q3 September 30, 2014 1.13% 1.20% 1.27% 1.35% 1.42%

Q4 December 31, 2014 1.07% 1.16% 1.26% 1.36% 1.45%

(18)

To the Board of Directors of Invesco National Trust Company

We have audited the accompanying financial statements of Invesco Stable Asset Trust (the “Trust”), which comprise the statement of assets and liabilities, including the schedule of portfolio investments, as of December 31, 2013 and the related statements of operations, of changes in net assets and the financial highlights for the year then ended. These financial statements and financial highlights are hereafter collectively referred to as “financial statements”.

Management’s Responsibility for the Financial Statements

Management is responsible for the preparation and fair presentation of the financial statements in accordance with accounting principles generally accepted in the United States of America; this includes the design, implementation and maintenance of internal control relevant to the preparation and fair presentation of financial statements that are free from material misstatement, whether due to fraud or error. Auditor’s Responsibility

Our responsibility is to express an opinion on the financial statements based on our audit. We conducted our audit in accordance with auditing standards generally accepted in the United States of America. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free from material misstatement.

An audit involves performing procedures to obtain audit evidence about the amounts and disclosures in the financial statements. The procedures selected depend on our judgment, including the assessment of the risks of material misstatement of the financial statements, whether due to fraud or error. In making those risk assessments, we consider internal control relevant to the Trust preparation and fair presentation of the financial statements in order to design audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Trust’s internal control. Accordingly, we express no such opinion. An audit also includes evaluating the appropriateness of accounting policies used and the reasonableness of significant accounting estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that the audit evidence we have obtained is sufficient and appropriate to provide a basis for our audit opinion.

Opinion

In our opinion, the financial statements referred to above present fairly, in all material respects, the financial position of Invesco Stable Asset Trust at December 31, 2013, and the results of its operations, changes in its net assets, and the financial highlights for the year then ended, in accordance with accounting principles generally accepted in the United States of America.

Other Matter

Our audit was conducted for the purpose of forming an opinion on the financial statements taken as a whole. The Schedule of Securities Purchased, Sold, or Matured is presented for purposes of additional analysis and are not a required part of the financial statements. The information is the responsibility of management and was derived from and relates directly to the underlying accounting and other records used to prepare the financial statements. The information has been subjected to the auditing procedures applied in the audit of the financial statements and certain additional procedures, including comparing and reconciling such information directly to the underlying accounting and other records used to prepare the financial statements or to the financial statements themselves and other additional procedures, in accordance with auditing standards generally accepted in the United States of America. In our opinion, the information is fairly stated, in all material respects, in relation to the financial statements taken as a whole.

Boston, Massachusetts March 31, 2014