- third–party recordkeeper
third–party rec·ord·keep·er /-'re-kərd-ˌkē-pər/ n: a party (as an accountant or bank) summoned to produce records pertaining to a tax investigation of another party◇ The original party is entitled to receive notice of and to challenge the issuance of a summons to a third-party recordkeeper.
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.