Use the Treasury regulation abbreviation

Error²Federal courts, Illinois courts21st and 22nd editions

Treasury regulations are cited as “Treas. Reg. § 1.72-16(a)”, not “Treasury Regulation 1.72-16(a)”; a temporary or proposed one carries its own prefix.¹

1. 1B12.1.4 Federal Tax Materials. Tables: T1.2 Federal Administrative and Executive Materials.
2. 2An error: the rule in note 1 allows one form, and this is not it.