26 CFR §20.6060-1

(a) In general. A person that employs one or more tax return preparers to prepare a return or claim for refund of estate tax under chapter 11 of subtitle B of the Internal Revenue Code, other than for the person, at any time during a return period, shall satisfy the recordkeeping and inspection requirements in the manner stated in § 1.6060-1 of this chapter. (b) Effective/applicability date. This section is applicable to returns and claims for refund filed after December 31, 2008.