Section 301.6231(c)-6 - Indirect method of proof of income(a)In general. The treatment of items as partnership items with respect to a partner whose taxable income is determined by use of an indirect method of proof of income will interfere with the effective and efficient enforcement of the internal revenue laws. Accordingly, partnership items of such a partner arising in any partnership taxable year ending on or before the last day of the taxable year of the partner for which a deficiency notice based upon an indirect method of proof of income is mailed to the partner shall be treated as nonpartnership items as of the date on which that deficiency notice is mailed to the partner.(b)Effective date. This section is applicable to partnership taxable years beginning on or after October 4, 2001. For years beginning prior to October 4, 2001, see § 301.6231(c)-6T contained in 26 CFR part 1, revised April 1, 2001.T.D. 8965, 66 FR 50561 , Oct. 4, 2001