To comply with IRS regulations, the American Heart Association receipts all donors of $250 or more.

Drop the "s" in "receipts".

To comply with IRS regulations, the American Heart Association receipt all donors of $250 or more. Better?

Change "donors" to donations.

To comply with IRS regulations, the American Heart Association receipt all dononations of $250 or more. Much better!

Add directive words and clauses.

In order to comply with IRS regulations the American Heart Association offers receipts for donations of $250 or more. Best.

(That nice sentence makes you want to send $250 just to get back a reciept, doesn't it?)