Investment Income Builder Fund

The Thornburg Investment Income Builder Fund, (the "Fund") did not declare capital gain dividends during 2016.

For the 2016 calendar year, 79.35% of the dividends paid from tax basis ordinary income (box 1a of Form 1099-DIV) qualify as qualified dividend income ("QDI") (box 1b of Form 1099-DIV) for the reduced tax rate under the American Taxpayers Relief Act of 2012.

21.61% of the ordinary income dividends paid by the Fund for 2016 (box 1a of Form 1099-DIV) qualify for the corporate dividends received deduction.

Foreign Taxes:

For the 2016 calendar year, the Fund has elected to pass-through its foreign withholding taxes to its shareholders. Your amount of foreign withholding taxes incurred by the Fund has been reported to you in box 6 on your Form 1099-DIV. Box 6 reports foreign income taxes paid on income derived from Fund investments in foreign securities. Federal tax rules generally permit U.S. taxpayers to either deduct or take a credit against their U.S. tax liability.

For the 2016 calendar year, 55.07% of the dividends paid from tax basis ordinary income (box 1a of Form 1099-DIV) is deemed to be foreign source income. The receipt of QDI may result in special rules in determining a taxpayer’s foreign tax credit limitation, as prescribed in Section 904 of the Internal Revenue Code.

Tax rules are complex. Please consult your tax advisor.

Important Information
Before investing, carefully consider the Fund’s investment goals, risks, charges, and expenses. For a prospectus or summary prospectus containing this and other information, contact your financial advisor or visit our literature center. Read them carefully before investing.

Investments carry risks, including possible loss of principal. Additional risks may be associated with investments outside the United States, especially in emerging markets, including currency fluctuations, illiquidity, volatility, and political and economic risks. Investments in small- and mid-capitalization companies may increase the risk of greater price fluctuations. Portfolios investing in bonds have the same interest rate, inflation, and credit risks that are associated with the underlying bonds. The value of bonds will fluctuate relative to changes in interest rates, decreasing when interest rates rise. Investments in the Fund are not FDIC insured, nor are they bank deposits or guaranteed by a bank or any other entity.

Thornburg mutual funds are distributed by Thornburg Securities Corporation.

Thornburg Investment Management, Inc. mutual funds are sold through investment professionals including investment advisors, brokerage firms, bank trust departments, trust companies and certain other financial intermediaries. Thornburg Securities Corporation (TSC) does not act as broker of record for investors.