A month-to-month tenancy is a periodic tenancy or lease in which the tenant is given possession of the leased premises with no specific expiration date and agrees to pay the landlord on a monthly basis. A month-to-month tenancy often requires the tenant or the landlord to give the other party 30 days written notice of termination of the lease.

Both residential leases and commercial leases may be month-to-month tenancies. If a residential or commercial tenant remains in the leased premises and continues to pay rent following the expiration of a lease for a longer term, there may be a new month-to-month tenancy created and recognized by law.

In Washington State, a month-to-month tenancy is recognized as a form of periodic tenancy where the tenant occupies the property without a definite lease term but continues to pay rent on a monthly basis. This arrangement does not have a set end date and can continue indefinitely until either the tenant or the landlord decides to terminate the tenancy. To end a month-to-month tenancy, Washington law generally requires the party wishing to terminate the lease to provide the other party with a written notice of at least 20 days before the rent is due. This is different from the commonly assumed 30-day notice period. This notice period applies to both residential and commercial month-to-month tenancies. If a fixed-term lease expires and the tenant remains in the property without signing a new lease but continues to pay rent, a month-to-month tenancy is often presumed to have been established under Washington law.