15 U.S.C. § 1639f: Requirements for prompt crediting of home loan payments

(a) In generalIn connection with a consumer credit transaction secured by a consumer’s principal dwelling, no servicer shall fail to credit a payment to the consumer’s loan account as of the date of receipt, except when a delay in crediting does not result in any charge to the consumer or in the reporting of negative information to a consumer reporting agency, except as required in subsection (b). (b) ExceptionIf a servicer specifies in writing requirements for the consumer to follow in making payments, but accepts a payment that does not conform to the requirements, the servicer shall credit the payment as of 5 days after receipt.