Can a Washington tenant use the security deposit as last month's rent?
No, unless the landlord agrees in writing. The security deposit is held to cover damages and unpaid rent at end of tenancy, NOT as a substitute for the final rent payment. A tenant who tries to apply the deposit toward last month's rent can be charged the full final rent in addition (since the deposit was not legally available for that purpose). Some Washington landlords may agree, but it must be in writing. The proper sequence: pay final month's rent, vacate, get the deposit back per RCW 59.18.280.
Source: RCW 59.18.280
This is an informational answer based on RCW 59.18.280 as of early 2026. It is not legal advice. Housing law changes year to year and local ordinances (especially in rent-controlled or rent-stabilized cities) can override or add to state law. For contested cases, consult a Washington-licensed attorney.