CO Rev. Stat. §10-16-704(4.5)(b-c)

(b) Except as otherwise provided in this subsection (4.5), adjustments to claims by the provider or the carrier shall be made within the time period set out in a contract between the provider and the carrier.  Such time period shall be the same for the provider and the carrier and shall not exceed twelve months after the date of the original explanation of benefits.

(c) Except as otherwise provided in this subsection (4.5), if there is no contract between a provider and a carrier, adjustments to claims paid to providers shall be made within twelve months after the date of the original explanation of benefits.  The time period for adjustments shall be the same for the provider and the carrier.