26 CFR §1.851-5

1. (a)Examples. The provisions of section 851 may be illustrated by the following examples:
2. (b)Effective/applicability dates. The rules of this section apply to quarters that begin on or after December 14, 2015. For purposes of applying the first sentence of section 851(d)(1) to a quarter that begins on or after March 14, 2016, the rules of this section apply in determining whether the taxpayer met the requirements of section 851(b)(3) and (c) at the close of prior quarters.