State Tax Day - Current, S.1, Colorado—Personal Income Tax: Individual Income Tax Guide Updated, (Feb 3, 2026)

Colorado updated its guidance on individual income taxes, providing details on taxation requirements for residents, part-year residents, and nonresidents earning Colorado-source income. The guidance discusses residency; calculation of tax; additions and subtractions from taxable income; withholding; estimated tax payments; filing and recordkeeping; refunds; and assessments.

Colorado Individual Income Tax Guide, Colorado Department of Revenue, January 2026, ¶201-654