Determining population of annexed territory — Certificate — As basis for allocation of state funds — Revised certificate.
RCW 35.13.260
in effect(1) Whenever any territory is annexed to a city or town, a certificate as hereinafter provided must be submitted to the office of financial management, hereinafter in this section referred to as "the office," within thirty days of the effective date of the action specified in the relevant ordinance. After approval of the certificate, the office shall retain the original copy and post a copy to the office of financial management website that is accessible to the public. The office must notify the department of transportation and the city or town that the certificate has been approved and posted, and include a link to the website. The certificates must be in a form and contain information as prescribed by the office. A copy of the complete ordinance containing a legal description and a map showing specifically the boundaries of the annexed territory must be included with the certificate. The certificate shall be signed by the mayor and attested by the city clerk. Upon request, the office shall furnish certification forms to any city or town. (2)(a) The resident population of the annexed territory shall be determined by, or under the direction of, the mayor of the city or town. (b) If the annexing city or town has a population of ten thousand or less, the annexed territory consists entirely of one or more partial federal census blocks, or 2010 federal decennial census data has not been released within twelve months immediately prior to the date of annexation, the population determination shall consist of an actual enumeration of the population. (c) In any circumstance, the city or town may choose to have the population determination of the entire annexed territory consist of an actual enumeration. However, if the city or town does not use actual enumeration for determining population, the annexed territory includes or consists of one or more complete federal census blocks, and 2010 federal decennial census data has been released within twelve months immediately prior to the date of annexation, the population determination shall consist of: (i) Relevant 2010 federal decennial census data pertaining to the complete block or blocks, as such data has been updated by the most recent official population estimate released by the office pursuant to RCW 43.62.030 ; (ii) An actual enumeration of any population located within the annexed territory but outside the complete federal census block or blocks; and (iii) If the office, at least two weeks prior to the date of annexation, confirms the existence of a known census error within a complete federal census block and identifies a structure or complex listed in (c)(iii)(A) through (E) of this subsection (2) as a likely source of the error, an actual enumeration of one or more of the block's identified: (A) Group quarters; (B) Mobile home parks; (C) Apartment buildings that are composed of at least fifty units and are certified for occupancy between January 1, 2010, and April 1, 2011; (D) Missing subdivisions; and (E) Closures of any of the categories in (c)(iii)(A) through (D) of this subsection. (d) Whenever an actual enumeration is used, it shall be made in accordance with the practices and policies of, and subject to the approval of, the office. (e) The city or town shall be responsible for the full cost of the population determination. (3) The population shall be determined as of the effective date of annexation as specified in the relevant ordinance. Until an annexation certificate is filed and approved as provided herein, such annexed territory shall not be considered by the office in determining the population of such city or town. Upon approval of the annexation certificate, the office shall forward to each state official or department responsible for making allocations or payments to cities or towns, a revised certificate reflecting the increase in population due to such annexation. Upon and after the date of the commencement of the next quarterly period, the population determination indicated in such revised certificate shall be used as the basis for the allocation and payment of state funds to such city or town. For the purposes of this section, each quarterly period shall commence on the first day of the months of January, April, July, and October. Whenever a revised certificate is forwarded by the office thirty days or less prior to the commencement of the next quarterly period, the population of the annexed territory shall not be considered until the commencement of the following quarterly period.
(1) Whenever any territory is annexed to a city or town, a certificate as hereinafter provided must be submitted to the office of financial management, hereinafter in this section referred to as "the office," within thirty days of the effective date of the action specified in the relevant ordinance. After approval of the certificate, the office shall retain the original copy and post a copy to the office of financial management website that is accessible to the public. The office must notify the department of transportation and the city or town that the certificate has been approved and posted, and include a link to the website. The certificates must be in a form and contain information as prescribed by the office. A copy of the complete ordinance containing a legal description and a map showing specifically the boundaries of the annexed territory must be included with the certificate. The certificate shall be signed by the mayor and attested by the city clerk. Upon request, the office shall furnish certification forms to any city or town.
(2)(a) The resident population of the annexed territory shall be determined by, or under the direction of, the mayor of the city or town.
(b) If the annexing city or town has a population of ten thousand or less, the annexed territory consists entirely of one or more partial federal census blocks, or 2010 federal decennial census data has not been released within twelve months immediately prior to the date of annexation, the population determination shall consist of an actual enumeration of the population.
(c) In any circumstance, the city or town may choose to have the population determination of the entire annexed territory consist of an actual enumeration. However, if the city or town does not use actual enumeration for determining population, the annexed territory includes or consists of one or more complete federal census blocks, and 2010 federal decennial census data has been released within twelve months immediately prior to the date of annexation, the population determination shall consist of:
(i) Relevant 2010 federal decennial census data pertaining to the complete block or blocks, as such data has been updated by the most recent official population estimate released by the office pursuant to RCW 43.62.030 ;
(ii) An actual enumeration of any population located within the annexed territory but outside the complete federal census block or blocks; and
(iii) If the office, at least two weeks prior to the date of annexation, confirms the existence of a known census error within a complete federal census block and identifies a structure or complex listed in (c)(iii)(A) through (E) of this subsection (2) as a likely source of the error, an actual enumeration of one or more of the block's identified:
(A) Group quarters;
(B) Mobile home parks;
(C) Apartment buildings that are composed of at least fifty units and are certified for occupancy between January 1, 2010, and April 1, 2011;
(D) Missing subdivisions; and
(E) Closures of any of the categories in (c)(iii)(A) through (D) of this subsection.
(d) Whenever an actual enumeration is used, it shall be made in accordance with the practices and policies of, and subject to the approval of, the office.
(e) The city or town shall be responsible for the full cost of the population determination.
(3) The population shall be determined as of the effective date of annexation as specified in the relevant ordinance.
Until an annexation certificate is filed and approved as provided herein, such annexed territory shall not be considered by the office in determining the population of such city or town.
Upon approval of the annexation certificate, the office shall forward to each state official or department responsible for making allocations or payments to cities or towns, a revised certificate reflecting the increase in population due to such annexation. Upon and after the date of the commencement of the next quarterly period, the population determination indicated in such revised certificate shall be used as the basis for the allocation and payment of state funds to such city or town.
For the purposes of this section, each quarterly period shall commence on the first day of the months of January, April, July, and October. Whenever a revised certificate is forwarded by the office thirty days or less prior to the commencement of the next quarterly period, the population of the annexed territory shall not be considered until the commencement of the following quarterly period.
Source: WA Statutes (Official Site)URL: https://app.leg.wa.gov/RCW/default.aspx?cite=35.13&full=trueFetched: 6/29/2026