Under the Fair Debt Collection Practices Act (FDCPA), a debt collector is defined as any person, company, or law firm that regularly collects, or attempts to collect, consumer debt for a creditor when the debt is in default.

Sometimes the creditor will assign collection of debt to a collector for a specific period of time. Other times, the creditor may sell the debt to a debt buyer (a company that buys old debt for the purpose of collecting it.) 

Usually, creditors that collect their own debts are not considered debt collectors under the FDCPA. But if the creditor uses a false name, it may be a debt collector.

Lawyers and repossession agents can also be debt collectors in some circumstances.