40 C.F.R. § 63.4140
You must complete the initial compliance demonstration for the initial compliance period according to the requirements in § 63.4141 . The initial compliance period begins on the applicable compliance date specified in § 63.4083 and ends on the last day of the first full month after the compliance date. If the compliance date occurs on any day other than the first day of a month, then the initial compliance period extends through the end of that month plus the next month. The initial compliance demonstration includes the determination according to § 63.4141 and supporting documentation showing that, during the initial compliance period, you used no coating with an organic HAP content that exceeded the applicable emission limit in § 63.4090 , and that you used no thinners or cleaning materials that contained organic HAP.
40 C.F.R. §63.4140