26 CFR § 1.1366-5 - Effective/applicability date.
(a) Sections 1.1366–1, 1.1366–2(a)(1), and 1.1366–2(b) through 1.1366–4 apply to taxable years of an S corporation beginning on or after August 18, 1998.
(b) Section 1.1366–2(a)(2) applies to indebtedness between an S corporation and its shareholder resulting from any transaction occurring on or after July 23, 2014. In addition, S corporations and their shareholders may rely on § 1.1366–2(a)(2) with respect to indebtedness between an S corporation and its shareholder that resulted from any transaction that occurred in a year for which the period of limitations on the assessment of tax has not expired before July 23, 2014.
(c) Sections 1.1366–2(a)(3) through (7), and this section apply on and after July 23, 2014. For rules that apply before that date, see 26 CFR part 1 (revised as of April 1, 2014).