D.C. Code § 47-1812.17: Furnishing copy of federal return.

For the purpose of determining the liability of any person under this chapter and the extent of such liability, the Mayor may require the taxpayer to furnish the District with a true and correct copy of such person’s federal income tax return, and a copy of any federal partnership return with respect to any or all partnerships in which the taxpayer has a proprietary interest, for any taxable year, and a reconciliation of such return with the taxpayer’s District return for such taxable year.