31 C.F.R. § 10.31 Negotiation of taxpayer checks.
Title 31 - Money and Finance: Treasury
A practitioner who prepares tax returns may not endorse or otherwise negotiate any check issued to a client by the government in respect of a Federal tax liability.
Title 31: Money and Finance: Treasury
PART 10—PRACTICE BEFORE THE INTERNAL REVENUE SERVICE
Subpart B—Duties and Restrictions Relating to Practice Before the Internal Revenue Service
§ 10.31 Negotiation of taxpayer checks.

