Say you receive a bill for a debt you don't owe: You already made the payment, or you never received the goods or services in question. While you may not owe the debt, you shouldn't ignore it. By law you have thirty days to dispute a debt in writing or a debt collector can assume that the debt is valid. To maintain your rights under the Fair Debt Collections Practices Act, always respond in writing to any debt that you dispute. Doing so keeps the creditor or debt collector from reporting the debt to credit bureaus – at least for some period of time – and also protects your legal rights.