Currently your tenants went from having a periodic tenancy, to a tenancy at sufferance (which is when a tenant wrongfully holds over after termination of the tenancy).

As a Washington landlord, you must follow certain procedures to terminate a tenancy. To terminate a periodic tenancy, a landlord must give at least 20 days' written notice prior to the end of the month. However, if the tenant violates his or her obligations, for example, by failing to pay the rent, the landlord may terminate the lease through eviction proceedings.

The action by a landlord to remove a tenant from a rental unit is known as an eviction or an "unlawful detainer."

In eviction actions strict rules and procedures must be observed. Generally, a legal eviction process involves:

1. Proper notice. Before evicting a tenant, you must serve the required eviction notices using proper procedures. Proper notice usually involves mailing, handing to the tenant, or posting on the unit, the notice.   This link should provide you with the forms that you can use: http://accessevictions.com/free-eviction-forms/

2. After you paste the notice, you can file the lawsuit if your tenant refuses to leave. Be aware that if the tenant disputes the reasons for the eviction, the tenant is entitled to a court hearing.

3. If you win, contact the Sheriff who would then be ordered to physically evict a tenant and remove the property in the unit. Only the sheriff, not the landlord, can physically remove a tenant who does not comply with an eviction notice and only after an unlawful detainer lawsuit has been filed.
   

Also, be aware that if you win the dispute, you will be able to collect for attorney fees as well.

Sincerely,

Dimitry Alexander Kaplun, Esq.