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Annexations and municipal boundary changes Q&A

Why does my city need Office of Financial Management (OFM) approval for an annexation?

State law, RCW 35.13.260 and RCW 35A.14.700, requires that annexation certificates be approved by OFM before the population and housing in an annexed area can be used for population purposes. All annexations and boundary line adjustments must have a certificate sent to OFM even if there is no population in the area.

Which documents do I need to send to OFM?

Please refer to the Annexation/Boundary Line Adjustment Documentation Checklist.

Are other documents sometimes needed?

Yes. Some annexations have unique conditions that require proof of accomplishment.

  • If the annexation goes to a boundary review board (BRB) after council passage, then a copy of the BRB letter indicating the end of its review needs to be included. Please refer to the Annexation Effective Dates document for more information.
  • If the ordinance requires an action be met in order for the annexation to be effective, proof of the action needs to be included. Examples include, but are not limited to, deeding a right-of-way, transferring water rights, site clearance, etc.

Why does OFM need a legal description?

OFM needs a legal description that can be used by Washington State Department of Transportation (WSDOT) cartography staff to plot the annexed area. The legal description needs to describe a specific area for OFM to approve for population purposes. The following actions are suggested:

  • After the legal description has been drafted, have someone other than the person who wrote the description plot it on a map as written.
  • Whenever possible, boundaries should be described in terms of a true point of beginning with bearings and distances, portions of sections or lines within sections, and other identifiable features such as "the North right of way line of 141st Street to the East right of way line of 53rd Avenue."
  • Tie the point of beginning to an identifiable feature such as a quarter corner, street intersection, or right-of-way intersection. If possible, do not start a description on a tax lot or a government lot or use government lots anywhere in the annexation claim as these can be difficult to plot.
  • If long abandoned rights-of-way are followed, include a copy of the plat, map or right-of-way plan.
  • Describe what is being annexed rather than what is not being annexed.
  • Avoid the use of abbreviations.

What should be included in the map of the annexed area?

The map does not have to show the entire city/town—just enough to be able to locate the annexed area in geographic space. OFM's preference is for the annexed area to be outlined in red and the city/town limits prior to the annexation in green. Street names should be present and legible. The map is not the legal definition of the property annexed.

My city plans to contract for an annexation census. What do I need to know?

Under statutes RCW 35.13.260, RCW 35A.14.700, and RCW 43.62.040, the count of population and housing in annexations or other boundary changes shall be made in "accordance with practices and policies, and subject to the approval of The Office of Financial Management". Therefore, when contracting for these services, local jurisdictions should ensure that the consultant, by contract, is required to follow OFM's guidance and that their work be acceptable to OFM who must approve the results. Failure to follow the proper process could result in cities having to recount the annexed population and housing, costing additional funds. It is highly recommended that OFM be notified in advance of which contractor is hired. If the contractor has not attended an OFM census administrator training session, arrangements need to be made for training. If you have questions, please contact us at

Can you tell me more about effective dates as they relate to ordinances, annexations, and resolutions for my city?

Ordinance effective date is when the law takes effect. Annexation effective date is when the annexed area legally becomes part of the city/town. A resolution is effective upon passage by municipal council. The majority of the time, ordinance effective date and annexation effective date are the same. In some cases, the law or local planning needs dictate that they be different. Please refer to the Annexation Effective Dates document for more information.

My city is interested in annexing a large population. What do I need to know?

The legislature passed RCW 82.14.415 to encourage cities to annex high cost areas. This incentive only applies to selected cities in King, Pierce, and Snohomish Counties. The area to be annexed must be in an annexation resolution on or before January 1, 2015. RCW 82.14.415 provides tax incentives for ten years after annexation to cities annexing areas of 10,000 or more population. Cities annexing under RCW 82.14.415 are required to count population according to RCW 35.13.260 and RCW 35A.14.700. Please refer to this document for more information.

Can you tell me more about annexation filing and how it relates to revenue distribution?

The annexation filing reports to the appropriate agencies the adjusted populations to be used in the next revenue distribution cycle. The specifics of the filing/revenue distribution cycle are:

  • Annexations are filed on the last working day of the months of November, February, May, and August. The filing includes all annexations approved by OFM during the months since the previous filing.
  • The adjusted populations are used for revenue distribution starting in the first month of the next calendar quarter (January, March, June, and September).
  • The November filing is the first report to use the newest April 1 population estimates (plus annexations approved after April 1).

There are three separate quarterly reports in the annexation filing that can be found on our website:

  • Approved annexations by city and ordinance.
  • Adjusted population by city (due to annexation/military adjustment).
  • A four-quarter summary of adjusted population by city.

Where should I mail my annexation or municipal boundary change documents?

Send all documentation listed on the checklist to:

Office of Financial Management
Forecasting and Research Division
P.O. Box 43124
Olympia, WA 98504-3124

If using FedEx, UPS, etc.:

Office of Financial Management
Forecasting and Research Division
1500 Jefferson St SE
Olympia, WA 98504-3124

Last updated
Wednesday, March 8, 2023
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