26 U.S.C. § 6232 — Assessment, collection, and payment

(a) General rule. An imputed underpayment is assessed and collected as if it were an adjustment-year tax under subtitle A, except that subchapter B of chapter 63 does not apply and an underpayment covered by section 6227(b)(1) may be paid and assessed when the administrative adjustment request is filed.
(b) Waiting period. Unless this subtitle provides otherwise, no assessment, levy^*, or court collection proceeding may occur before (1) the 90th day after mailing the final-adjustment notice and (2), if a section 6234 petition is filed, the court decision becomes final. This waiting rule does not apply to a specified similar amount under subsection (f)(2).
(c) Injunction. Despite section 7421(a), a proper court, including the Tax Court^*, may stop an action violating subsection (b). The Tax Court may do so only if a timely section 6234 petition was filed and only for adjustments in that petition.
(d) Exceptions. (1)(A) If notified that a partnership^*-return mathematical or clerical error requires an adjustment, rules similar to section 6213(b)(1) and (2) apply. (B) If a partnership is a partner^* and failed section 6222(a) for its interest in another partnership, that adjustment is treated the same way, except section 6213(b)(2) does not apply. (2) At any time, whether or not a notice exists, the partnership may waive these subsection (b) restrictions in a signed written notice filed with the Secretary^*.
(e) If no section 6234 proceeding begins during subsection (b)’s 90 days, the partnership’s section 6225 liability cannot exceed the notice amount.
(f) Failure to pay. (1) If an applicable imputed underpayment, specified similar amount, interest, or penalty remains unpaid 10 days after notice and demand, (A) the section 6621(a)(2)(B) rate is calculated with 5 rather than 3 percentage points, and (B) the Secretary may assess each partner at the adjustment year’s end, or former partners if the partnership ended, a tax equal to that partner’s proportionate share, including adjusted interest and penalties. (2) “Specified similar amount” means (A) the amount in section 6226(b)(4)(A)(ii)(II), including a failure treated under section 6651(i) as failure to pay it, and (B) an amount assessed under paragraph (1)(B) against a partnership partner. (3) The Secretary determines each share from the partner’s distributive share, and all shares^* together must equal 100%. (4) Partnership liability falls when a partner pays; paragraph (1)(B) no longer applies after the partnership pays. (5) An S corporation^* and shareholders^* are treated as a partnership and partners. (6)(A) Subchapter B does not apply to assessment or collection under this paragraph. (B) Unless this subtitle provides otherwise, assessment or a court proceeding without assessment against a partner for paragraph (1) amounts must begin within two years after the notice and demand.