3 Colo. Code Regs. § 702-3-1-5-4
Each taxpayer seeking to claim a credit or refund of premium tax must file the tax form prescribed by the commissioner of insurance. Each such filing must be for the calendar year, and such filing must be received on or before March 1. In addition to the prescribed form, when an enterprise zone credit or refund is sought, a supplementary schedule must be attached to the tax form. This schedule shall itemize and describe each claim for credit or refund and include a statutory citation referencing the pertinent section of Article 30 of Title 39, Colorado Revised Statutes that permits each claim or refund. This schedule shall be attested to by an officer of the company and contain, in a prominent location, the full company name, NAIC company number (if any), corporate seal, printed name and title of officer attesting to the correctness of the claim.
The value of the credit sought shall be further supported by an original certificate issued by the enterprise zone administrator. This certification shall set forth both the value and purpose of the related expenditure for which credit or refund is sought.
3 CCR 702-3-1-5-4