26 USC 346 - Definition and special rule

(a) Complete liquidation 
For purposes of this subchapter, a distribution shall be treated as in complete liquidation of a corporation if the distribution is one of a series of distributions in redemption of all of the stock of the corporation pursuant to a plan.
(b) Transactions which might reach same result as partial liquidations 
The Secretary shall prescribe such regulations as may be necessary to ensure that the purposes of subsections (a) and (b) of section 222 of the Tax Equity and Fiscal Responsibility Act of 1982 (which repeal the special tax treatment for partial liquidations) may not be circumvented through the use of section 355, 351, or any other provision of law or regulations (including the consolidated return regulations).