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Planning for Annexation

This page provides an overview of how cities in Washington State can prepare for annexation, including the annexation planning process, zoning newly annexed territory, tools/studies used to evaluate annexation proposals, and community outreach and engagement programs.

It is part of MRSC's series on Annexation in Washington State.

New legislation: Effective July 23, 2023, 2SHB 1425:

  • Requires an interlocal agreement for annexed areas in which a sales and use tax is imposed to address certain specified criteria.
  • Removes the requirement that a city commence annexation prior to January 1, 2015, to be eligible for the sales and use tax credit.
  • Changes population thresholds for imposing the sales and use tax for annexed areas.


There is no “one-size-fits-all” approach to pursuing a single annexation or an overall annexation strategy, however nearly all annexations require significant planning and community outreach. There are several issues to consider when a city is contemplating annexing territory, including zoning/development review, community character, fiscal impacts, impacts on overlapping special purpose districts, and when and how to extend urban services.

There are also limitations on annexation. Some important limitations to keep in mind are:

The following sections briefly describe components of the annexation planning process, as well as the tools commonly used by cities during that process, including examples. For more detailed explanations of steps in the planning process, see our Annexation for Cities and Towns publication. For Frequently Asked Questions regarding planning for annexation, see our Annexation FAQs.

Annexation Comprehensive Planning and Strategies

Many jurisdictions have incorporated annexation planning into their comprehensive planning process, and some have developed specific and targeted annexation strategies. Many have coordinated with neighboring cities and the relevant county/counties using interlocal agreements to ensure coordinated growth and effective transitions to incorporation.

Cities within GMA Planning Counties

The Growth Management Act (GMA) imposes planning requirements that influence the ability of a city to annex and the territorial extent of its authority to annex. A city, in coordination with the county, must identify urban growth areas, and annexation may only occur within these designated urban growth areas.

As part of its comprehensive planning responsibilities under the GMA, a city must have adopted policies dealing with land use, housing, capital facilities, utilities, and transportation (RCW 36.70A.070). These policies must also address lands within the city’s urban growth area, because the city will be the provider of urban-type services in that area upon annexation to the city.

The GMA also requires that counties adopt, in cooperation with the cities in the counties, county-wide planning policies (CPPs) that must include, among other things, “policies for joint county and city planning within urban growth areas.” (RCW 36.70A.210(3)(f)).

Consequently, cities in GMA counties will evaluate annexation in the context of their GMA comprehensive planning responsibilities. Cities often include in their comprehensive plans an “annexation element” to provide policy guidance for annexation of territory within urban growth areas. Many cities, in coordination with counties, also identify “potential annexation areas” which aid in planning, as well as coordination with neighboring cities. See RCW 36.70A.110(7).

Examples of Annexation Elements in City Comprehensive Plans

Examples of City Annexation Plans and Strategies

Cities within Non-GMA Planning Counties

Cities in non-GMA planning counties are not required to adopt a comprehensive plan; and urban growth areas may not be designated. A comprehensive plan (if any) may not address annexation. Nevertheless, it is important to establish guidelines or criteria to be able to assess whether individual annexation proposals are consistent with the overall vision and goals for the particular city. Although in a non-GMA planning county, Winthrop's Comprehensive Plan includes an Annexation and Growth Element.

Pre-Annexation Zoning

Until an area is officially annexed, it remains subject to the county’s regulations, including its development regulations. The annexation statutes give cities in both GMA and non-GMA planning counties the authority to adopt zoning regulations for areas outside of its city limits in areas it may reasonably expect to annex (for non-code cities, see RCW 35.13.177 and 35.13.178; for code cities, see RCW 35A.14.330 and 35A.14.340). While these regulations won’t apply until territory is officially annexed, doing this provides a more seamless transition for when an area is ultimately incorporated.

Example of Pre-Annexation Zoning

As an alternative to this process set forth in the annexation statutes, municipal codes may outline the procedures for how a city will zone and plan for areas to be annexed.

Examples of Code Provisions for Zoning Annexed Areas

There are times when a jurisdiction will not have pre-planned for a particular annexation. In these circumstances, jurisdictions may take different approaches. For a discussion of these approaches, including some important legal considerations, see Zoning for Annexation in Areas Not "Prezoned" in our Annexation Publication.

Development Agreements

Cities have authority to enter into pre-annexation development agreements with developers or landowners within a potential annexation area pursuant to RCW 36.70B.200. A development agreement will set the terms of development for a landowner or landowners upon annexation, sometimes in exchange for an agreement to annex.

Examples of Annexation-Related Development Agreements

Coordination with Counties – Interlocal Agreements

Jurisdictions affected by annexations will need to coordinate to ensure orderly transition from county to city governance. The GMA, the Interlocal Cooperation Act, and annexation statutes all contemplate such coordination. An Interlocal Agreement is one way to achieve a smooth and successful transition of governance. These agreements can cover a range of topics including zoning/development review, transition of services, and revenue issues.

Examples of Interlocal Agreements

Note: Some statutory annexation methods are achieved by the city and county (and sometimes fire protection districts) entering into Interlocal Agreements (for example, RCW 35A.14.460 and RCW 35A.14.296). To learn more about these interlocal agreement annexation methods and to see examples of ILAs entered into pursuant to those provisions, see the Annexation Methods page.

Evaluating Specific Annexation Proposals (Including Fiscal Impact Analyses)

There are many potential consequences to annexation, and cities should carefully evaluate individual annexation proposals to fully understand those consequences prior to a decision to annex. For a detailed discussion, see Consequences of Annexation in our Annexation publication.

Comprehensive Studies and Fiscal Impact Analyses

Depending on their size and complexity, cities may prepare fiscal impact analyses and/or comprehensive annexation studies to evaluate the impacts of proposed annexations. These are often detailed reports prepared by consultants. Below are several examples.

Examples of Comprehensive Annexation Studies and Fiscal Impact Analyses

Public Engagement / Information Campaigns

Successful annexations require successful public engagement and information campaigns. Cities should educate their residents and impacted landowners about the potential benefits and burdens associated with a decision to annex. Cities will often maintain webpages or prepare information pamphlets to inform interested parties about potential annexations. Below are some examples of materials used in these public engagement/information campaigns.

Examples of Information Programs

Impacts on Overlapping Special Purpose Districts

If special purpose district boundaries overlap with territory to be annexed by a city or town, state law generally describes the consequences for both the district and city. For a detailed discussion and statutory references, see our Annexation publication section on Consequences of Annexation on Special Purpose Districts.

Last Modified: June 26, 2023