You have the right to ask a debt collector to send proof of a debt as long as you make the request within the first 30 days of being contacted. (debtsettlement.com)
Although you will need to provide proof of debt and income, the majority of work falls back on the legal professional. (bankruptcy-america.com)
The credit bureaus have to make contact with the collection agency and will request proof of the debt owed. (creditrepair.org)