It sounds like you're referring to under the APTC (Association of Public Treasurers of Canada/US or related tax/benefit context) — though most commonly, APTC refers to Advance Premium Tax Credit under the US Affordable Care Act (ACA).
However, I suspect you might be thinking of a different — perhaps a state or local reconciliation form? Could you clarify which jurisdiction or program this is for? aptc form 58 -excel format-