12 CFR §1006.100

1. (a)In general. Except as provided in paragraph (b) of this section, a debt collector must retain records that are evidence of compliance or noncompliance with the FDCPA and this part starting on the date that the debt collector begins collection activity on a debt until three years after the debt collector's last collection activity on the debt.
2. (b)Special rule for telephone call recordings. If a debt collector records telephone calls made in connection with the collection of a debt, the debt collector must retain the recording of each such telephone call for three years after the date of the call.