The maximum duration of a standard residential lease agreement is one (1) year in Washington. Leases for longer than one year are permissible, but they are subject to certain laws.
Leases for one year or longer must be in writing, and they must be notarized in order to be valid and binding. Leases for a shorter duration are valid as well, but they must also be in writing to be valid. However, they do not have to be notarized.
Verbal rental agreements are allowed, but only for month-to-month leases. If the landlord collects a fee, the rental agreement must be in writing (WA Rev Code § 59.18.285).
The information for this answer was found on our Washington Residential Lease Agreement answers.