US Fair Debt Collection Practices Act (FDCPA) and Regulation F (12 CFR Part 1006) 1692h: Apply a single payment on multiple debts as the consumer directs and never to a disputed debt

Where a consumer who owes several debts makes one payment to a debt collector, the collector may not apply it to any debt the consumer disputes and, where the consumer gives directions, must apply it in accordance with those directions.