In Washington state, it is best to have a written lease. Oral leases are valid, but they can be enforced only as leases from month to month. A lease for longer than month to month must be in writing. Per RCW § 59.04.010, if the lease is longer than one year, the execution of the lease must be acknowledged (i.e. notarized).

If a lease is longer than one year and it is not acknowledged, then it may be interpreted to be only a month to month lease, not a one-year lease. This may also apply to unacknowledged one-year leases with any options to renew.

To summarize, it is the best practice to do the following in Washington:

  1. Always have a written lease.
  2. For any lease longer than one year, acknowledge (notarize) the signatures of both parties.
  3. For any lease one-year or less that has renewal options that would extend the term of the lease beyond one year, acknowledge (notarize) the signatures of both parties.

While few states require acknowledgement, Washington is not alone. Florida also requires notarization for leases longer than one year, but Florida's requirement applies to only the landlord's signature.