Washington Rent Increase Cap 2027: Maximum Increase in Any 12-Month Period Is 10%

The statutory formula sets the cap at 7% plus the Consumer Price Index, or 10%, whichever is less.

[Cite: RCW 59.18.700, as established by H.B. 1217, 2025 Wash. Sess. Laws, c. 209]

That "whichever is less" structure means the cap isn't simply whatever the CPI-based calculation produces; it's bounded by an absolute statutory ceiling of 10%, regardless of how high inflation or the CPI component might otherwise push the formula's raw output.

The actual 7%-plus-CPI calculation for the relevant period came out to 11.53%, but since that exceeds the 10% statutory maximum, the lower 10% figure applies instead.

[Cite: RCW 59.18.700; Wash. Dept. of Commerce, 2027 rent increase cap announcement, July 15, 2026]

That outcome illustrates exactly how the "whichever is less" mechanism functions in practice; a landlord doing the formula math independently and arriving at something above 10% should recognize the statutory ceiling, not that higher calculated number, is what actually governs.

The CPI component behind the 11.53% calculation was measured over the 12-month period from June 2025 through June 2026.

[Cite: Wash. Dept. of Commerce, 2027 rent increase cap announcement]

That specific measurement window is what the Department of Commerce uses to calculate each year's applicable cap; a landlord trying to understand why a given year's cap landed where it did should look at inflation data over that same defined 12-month window, not a different or more recent period.

The statute itself sets the formula; the Department of Commerce is the entity responsible for calculating and publishing the actual applicable percentage each year based on that formula.

[Cite: RCW 59.18.700]

That division of responsibility means a landlord looking for the current year's specific cap percentage should check the Department of Commerce's published figure directly, rather than trying to independently recalculate it from raw CPI data, since Commerce's published number is the authoritative source landlords and tenants actually rely on.

The cap governs the maximum rent increase for any 12-month period, not simply increases imposed at the start of a calendar year.

[Cite: RCW 59.18.700]

A landlord raising rent at any point during 2027 needs to measure that increase against whatever rent was in effect 12 months earlier, applying the 10% ceiling to that full 12-month comparison, rather than assuming the cap only governs increases that happen to land on January 1.

Washington's 2026 rent increase cap was set at 9.683%, a different figure from this year's 10% ceiling.

[Cite: RCW 59.18.700; Wash. Dept. of Commerce, 2026 rent increase cap announcement]

That year-over-year difference is built into how the formula works; since the cap is recalculated annually based on the relevant period's CPI data, a landlord should expect the applicable percentage to change from year to year, sometimes landing below the 10% ceiling, sometimes hitting it exactly, as happened for 2027.

Since this percentage is recalculated and republished annually rather than fixed permanently in statute, a landlord needs to check the Department of Commerce's current published figure before finalizing any rent increase, rather than relying on a prior year's cap.

[Cite: RCW 59.18.700]

A landlord planning a 2027 rent increase based on an outdated 2026 figure risks either underpricing relative to what's actually allowed, or, more seriously, planning an increase that exceeds whatever the current year's actual published cap turns out to be.

This percentage cap is one piece of House Bill 1217's broader framework, which also includes a 90-day rent-increase notice requirement delivered on a specific state form.

[Cite: RCW 59.18.700; H.B. 1217, 2025 Wash. Sess. Laws, c. 209]

A landlord planning a rent increase within this 10% cap still has to separately satisfy that 90-day notice requirement using the correct statutory form; staying within the percentage cap alone doesn't substitute for meeting the law's separate notice and timing obligations.

Since the cap applies to any 12-month period rather than a fixed calendar window, a landlord benefits from clearly documenting exactly which 12-month period and prior rent figure a given increase is being measured against.

[Cite: RCW 59.18.700]

A landlord who can show precisely which earlier rent figure and date a current increase is being compared to is in a much stronger position if a tenant or regulator later questions whether a specific increase actually stayed within the applicable cap.

A landlord planning to raise rent at the start of calendar year 2027 should apply this 10% cap immediately, while a landlord planning a later 2027 increase should still confirm this remains the correctly applicable published figure at the time of that later increase.

[Cite: RCW 59.18.700]

Since Commerce republishes this figure annually, a landlord executing a rent increase later in 2027 should still be working from this same calendar-year-2027 published cap, but should confirm no updated guidance has superseded it before finalizing that later increase.

The practical starting point is updating internal rent-increase planning tools and templates to reflect the 10% maximum for any 12-month period in 2027, replacing whatever cap applied in 2026.

Building a standard process for checking the Department of Commerce's published figure at the start of each calendar year, rather than relying on institutional memory of a prior year's number, keeps a portfolio's rent-increase planning aligned with the correct, currently applicable cap going forward.