The Growth Management Act (GMA) requires that certain counties, and the cities within those counties, engage in planning for future population growth.  Counties that have a population of 50,000 or more and, prior to May 16, 1995, had its population grow by 10 percent or more in the ten years prior to 1995, or, after May 16, 1995, by 17 percent or more in a subsequent 10 year period, are covered by the GMA.  So, too, is any county that experiences population growth of 20 percent over a ten-year period.  Counties with populations under 50,000, that would otherwise be required to plan, can remove themselves from the GMA's comprehensive planning requirements.  Conversely, counties that do not meet the standards for automatic inclusion in the GMA may choose to be included.

Currently, 18 counties are required to plan, 10 have chosen to plan, and 11 are not subject to the full GMA planning requirements.

Whether a county is automatically required to plan under the GMA or voluntarily chooses to, the planning requirements are largely the same, and the comprehensive plan is the centerpiece of the process.  The Legislature has established 14 goals to act as the basis of all comprehensive plans.  Examples of goals include reducing sprawl, providing for affordable housing, and protecting property rights.  The comprehensive plan must address these goals and set out the policies and standards that are meant to guide the county's or city's actions and decisions in the future.  Comprehensive plans must contain certain elements, such as a land use element, a housing element, and a capital facilities plan element.  These elements must satisfy the requirements for each individual element while fitting within the overall comprehensive plan.

Every 10 years, a county or city that is planning under the GMA must review and revise its comprehensive plan and development regulations to ensure that the plan and regulations comply with the requirements of the GMA.  This review and revision requires legislative action from the county or city. 

The 10-year review and revision deadlines are staggered for different counties.  Currently, King, Kitsap, Pierce, and Snohomish counties, and the cities within those counties, have a deadline of December 31, 2024.  Clallam, Clark, Island, Jefferson, Lewis, Mason, San Juan, Skagit, Thurston, and Whatcom counties, and the cities within those counties, have a deadline of June 30, 2025.  Benton, Chelan, Cowlitz, Douglas, Franklin, Kittitas, Skamania, Spokane, Walla Walla, and Yakima counties, and the cities within those counties, have a deadline of June 30, 2026.  Finally, Adams, Asotin, Columbia, Ferry, Garfield, Grant, Grays Harbor, Klickitat, Lincoln, Okanogan, Pacific, Pend Oreille, Stevens, Wahkiakum, and Whitman counties, and the cities within those counties, have a deadline of June 30, 2027.  

Each of these counties, and the cities within them, must again update their comprehensive plans every 10 years after the current deadline, except for the first group of counties and cities, which will change to a deadline of June 30, 2034, for its next update after 2024, and will have a deadline every 10 years after that date going forward.

The next comprehensive plan review and revision deadline for Clallam, Clark, Island, Jefferson, Lewis, Mason, San Juan, Skagit, Thurston, and Whatcom counties, and the cities within those counties, is December 31, 2025.  The following comprehensive plan review and revision deadline for these counties and cities is June 30, 2035, with subsequent reviews and revisions required every 10 years after that date.