Special District Grant Accessibility Act This bill requires the Office of Management and Budget (OMB) to issue guidance within 180 days that clarifies how a federal agency recognizes a special district as a unit of local government for the purpose of being eligible to receive federal financial assistance. Under the bill, a special district is a political subdivision of a state, with specified boundaries and significant budgetary autonomy or control, that was created by or pursuant to state law to perform limited and specific governmental or proprietary functions that distinguish it as a significantly separate entity from the administrative governance structure of any other form of local government unit within a state. The bill requires federal agencies to implement OMB's guidance within one year of the date it is issued.