26 CFR § 301.6314-1 - Receipt for taxes.
(a) In general. The district director or the director of a service center shall upon request, issue a receipt for each tax payment made (other than a payment for stamps sold and delivered). In addition, the district director or the director of a service center shall issue a receipt for each payment of 1 dollar or more made in cash, whether or not requested. In the case of payments made by check, the canceled check is usually a sufficient receipt. No receipt shall be issued in lieu of a stamp representing a tax, whether the payment is in cash or otherwise.
(b) Duplicate receipt for payment of estate taxes. Upon request, the district director or the director of a service center will issue duplicate receipts to the person paying the estate tax, either of which will be sufficient evidence of such payment and entitle the executor to be credited with the amount by any court having jurisdiction to audit or settle his accounts. For definition of the term “executor”, see section 2203.