Guides · Washington · Landlords + renters
Washington's 2026 rent cap: the exact math and five ways notices still fail
See the official 9.683% Washington rent-cap calculation for 2026 and the amount, timing, form, service, and exemption checks a notice still needs.
Washington's standard 2026 rent-increase limit is 9.683% for covered residential tenancies. That is a published statewide figure, not a round-number estimate. It comes from the statutory formula of seven percent plus the June twelve-month change in the Seattle-area CPI-U, subject to a ten-percent ceiling.
The percentage is only the amount test. A notice can still fail because it is issued during the first twelve months, provides too little time, uses the wrong form, is delivered incorrectly, or claims an exemption without the required supporting facts. RentCap checks those questions separately so a good percentage cannot hide a defective notice.
The 9.683% calculation
Washington Commerce lists a June 2024 CPI-U index value of 354.824 and a June 2025 value of 364.344 for the Seattle-Tacoma-Bellevue series specified by RCW 59.18.700. The change is about 2.683%. Adding the statutory seven percentage points produces 9.683%, which is below the separate ten-percent ceiling. Commerce therefore published 9.683% as the maximum standard increase through December 31, 2026.
For a current monthly rent of $1,800, multiplying by 1.09683 produces $1,974.294. A landlord still has to choose a payable amount and follow every other rule; the formula does not authorize an automatic increase or cure a bad notice. Manufactured or mobile-home lot rent uses a separate five-percent path, and exemptions can change which row applies.
Failure one: treating the cap as permission
RCW 59.18.700 bars a covered increase during the first twelve months after the tenancy begins. After that first year, it also limits increases during a twelve-month period. That means the correct annual percentage can still be too early. The tenancy start date, prior increase history, and planned effective date belong in the calculation.
A lease does not disappear from the analysis either. Washington's notice statute says an increase generally cannot take effect before the rental agreement term is complete. The practical question is not only how high the new rent may be, but when that particular tenancy can reach it.
Failures two and three: timing and the required form
The statewide baseline is at least ninety days' prior written notice for many residential increases. Seattle and Tacoma can add local questions, and a rent-cycle start date can push the clean effective date beyond the first day that merely satisfies a day count. Counting from an assumed mailing date instead of the actual service facts is a common source of error.
Washington also prescribes substantially the same notice form in RCW 59.18.720. The notice tells the tenant the current rent, new rent, percentage, effective date, cap information, exemption claim where applicable, and enforcement information. A casual letter that contains only the new dollar amount is not a substitute for checking the required form.
Failures four and five: service and exemption facts
RCW 59.12.040 provides specific service paths. Personal delivery is one path. Substitute service and posting paths require the additional acts described by the statute; simply emailing a PDF or leaving an envelope without completing the paired steps is not the same thing. HB 2664 changed the mailed-copy language in June 2026, but it did not turn every delivery method into valid service.
A landlord relying on the twelve-year building exemption or another exemption must include facts supporting the claim in the notice. A checkbox or unexplained label is weak evidence. The certificate-of-occupancy date, ownership facts, or program status should be reviewed against the specific exemption before the increase is served.
A safer workflow
Start with the current rent, proposed rent, tenancy start date, prior increase history, property type, and exact city. Then identify the planned service date and method. Review exemption facts only after the standard path is visible; otherwise an uncertain exemption can prematurely erase the rules that would apply if the claim is wrong.
RentCap's free check shows the amount and timing findings with official sources. For landlords, the $19 packet uses the supported amount and date to prepare a notice draft, calculation worksheet, delivery instructions, proof log, calendar file, and archive PDF. It is a self-help compliance tool, not a law firm, and unusual facts should be reviewed with qualified counsel.
Questions the published number does not answer
The Commerce percentage does not decide whether a charge is rent, whether the tenant has already had an increase in the relevant twelve-month period, or whether a subsidized or affordable program imposes a lower limit. It also does not prove that a city, lease, or funding source permits the proposed date. Those facts belong in the file before the number is presented as a maximum.
For a portfolio, run the calculation per unit rather than applying one spreadsheet percentage to every resident. Tenancy start dates, prior notices, certificates of occupancy, lease terms, cities, rent-cycle days, and service methods can differ inside one building. A batch process is safe only when it preserves those unit-level facts and exceptions.
Official sources
- Washington Commerce 2026 calculation
- RCW 59.18.700 — amount limits and remedies
- RCW 59.18.140 — notice timing
- RCW 59.18.720 — required notice form
- RCW 59.12.040 — service
RentCap is a self-help compliance tool, not a law firm. Sources can change; use the linked government text and the site's source changelog for the current verification date.
Related Washington guides
HB 2664 changed Washington rent-notice delivery: what the 2026 rule saysWashington's 12-year rent-cap exemption: which buildings qualifySeattle landlords: RRIO compliance can gate a rent increaseHow much can my landlord raise my rent in Washington in 2026? All guides