Subpart D - Miscellaneous Provisions

26 USC 6020 - Returns prepared for or executed by Secretary

(a) Preparation of return by Secretary 
If any person shall fail to make a return required by this title or by regulations prescribed thereunder, but shall consent to disclose all information necessary for the preparation thereof, then, and in that case, the Secretary may prepare such return, which, being signed by such person, may be received by the Secretary as the return of such person.
(b) Execution of return by Secretary 

(1) Authority of Secretary to execute return 
If any person fails to make any return required by any internal revenue law or regulation made thereunder at the time prescribed therefor, or makes, willfully or otherwise, a false or fraudulent return, the Secretary shall make such return from his own knowledge and from such information as he can obtain through testimony or otherwise.
(2) Status of returns 
Any return so made and subscribed by the Secretary shall be prima facie good and sufficient for all legal purposes.

26 USC 6021 - Listing by Secretary of taxable objects owned by nonresidents of internal revenue districts

Whenever there are in any internal revenue district any articles subject to tax, which are not owned or possessed by or under the care or control of any person within such district, and of which no list has been transmitted to the Secretary, as required by law or by regulations prescribed pursuant to law, the Secretary shall enter the premises where such articles are situated, shall make such inspection of the articles as may be necessary and make lists of the same, according to the forms prescribed. Such lists, being subscribed by the Secretary, shall be sufficient lists of such articles for all purposes.