Colorado Lease Termination Notice: 21 Days for Month-to-Month, 91 Days for Yearly

Colo. Rev. Stat. § 13-40-107 sets the written notice to terminate a tenancy without cause, scaled by tenancy length: "A tenancy for one year or longer, ninety-one days; a tenancy of six months or longer but less than a year, twenty-eight days; a tenancy of one month or longer but less than six months, twenty-one days; a tenancy of one week or longer but less than one month, or a tenancy at will, three days." The notice must state the property and the termination date, and a fixed-term lease ends on its own date unless renewed. Breaking a fixed lease early without statutory grounds can expose a tenant to remaining rent, subject to the landlord's duty to mitigate. Active-duty servicemembers may terminate under the federal Servicemembers Civil Relief Act.

A termination notice that gives less than the statutory period is defective and cannot support an eviction. There is no fixed statutory monetary penalty for an improper no-fault notice; the practical consequence is that the eviction fails and must be re-served with proper notice. Early lease-breaking liability is governed by the lease and the mitigation duty.