D.C. Code § 47-1006
The use and occupancy of real property in the District of Columbia by any department, agency, or instrumentality of the United States of America, or by the American Red Cross, on a basis which does not result in the receipt of rent or income to the owner thereof within the meaning of § 47-1005, shall not operate to terminate the tax-exempt status of such property if exempted from taxation prior to such use and occupancy; and, further, that any taxes, penalties, or interest which may be due by reason of such change in the use and occupancy of such property and unpaid on November 30, 1945, shall be abated; provided, that nothing contained in this section shall be construed as authorizing any refund of any taxes, penalties, or interest paid prior to November 30, 1945.
D.C. Code § 47-1006