26 CFR 40.6011(a)-2 - Final returns.
(a) In general - (1) Permanent cessation of operations. Any person that is required under § 40.6011(a)-1 to make returns and that permanently ceases all operations with respect to which liability for tax was incurred (or with respect to which tax had to be collected and paid over) must make a final return in accordance with the instructions applicable to the form on which the return is made. A person does not make a final return if only a temporary or partial cessation of such operations occurs and must continue to file returns as required under § 40.6011(a)-1.
(2) Change in law without cessation of operations. Any person that is required under § 40.6011(a)-1 to make returns must make a final return in accordance with the instructions applicable to the form on which the return is made if, by reason of a change in law, that person is no longer liable for any tax (or, in the case of a collected tax, is no longer responsible for collecting and paying over any tax). For example, if the tax on a product is changed from a retail tax to a manufacturers tax, a retailer formerly liable for the tax but now buying the product tax-paid from its supplier must make a final return (assuming that the retailer has no other tax liability reportable on the return).
(b) Special rule for one-time filings - (1) In general. A first return is also a final return if it is a one-time filing. A return is a one-time filing if the person reporting tax does not engage in any activity with respect to which tax is reportable on the return in the course of a trade or business.
(2) Deposits not required. See § 40.6302(c)-1(e)(2) for a rule providing that no deposit of taxes reported on a one-time filing is required.
(c) Special rule for floor stocks taxes. A first return reporting only floor stocks taxes under this part 40 is also a final return.