26 U.S.C. § 6303 — Notice and demand for tax

(a) Unless this title provides otherwise, within 60 days after assessing a tax under section 6203, the Secretary^* must as soon as practicable notify each person liable for the unpaid tax, state the amount, and demand payment. The notice must be left at the person’s home or usual business place or mailed to the person’s last known address. (b)(1) Unless the Secretary believes delay would endanger collection, if a tax is assessed before its payment deadline, payment may not be demanded under (a) until after that deadline. (2) The deadline is determined after counting any period disregarded under section 7508A because of a disaster, major fire, terrorist action, or military action.