Plumbing Contractor Permit Requirements in Seattle, WA

Complete permit and license guide for starting a plumbing contractor in Seattle, King County, Washington.

Updated 2026-02-15 6 stops $800–$2,500 est. 6–10 weeks to obtain all licenses and permits
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Not legal advice. Requirements may change — always verify with your local government authority before applying. This guide was compiled from public and official sources (last updated ) and has not yet been independently source-verified — confirm each requirement before acting on it.

Federal — start here

1 stop

  1. EIN (Employer Identification Number)

    Required if you have employees or operate as an LLC/corporation. Free from the IRS.

    Official government source

    FreeImmediate (online application)

State of Washington

3 stops

  1. Washington State Contractor Registration

    All contractors in Washington State must register with the Washington State Department of Labor and Industries (L&I). Contractor registration requires proof of general liability insurance ($50,000 minimum for specialty contractors), a $12,000 surety bond, and a unified business identifier (UBI) number from the Department of Revenue.

    Official government source

    $113 biennial registration fee + $12,000 bond (~$100–$250/year premium)1–3 weeks

  2. Washington State Plumber License

    Washington requires all plumbers performing work to hold a state Journeyman or Master Plumber license. The licensing qualifier for a plumbing contracting business must hold a state Plumbing Contractor License. Issued by the Washington State Department of Labor and Industries (L&I). Pass a state exam and have requisite experience.

    Official government source

    $135 (biennial plumber license); $175 (contractor license)4–8 weeks

  3. Washington Business Entity Registration

    LLCs and corporations must register with the Washington Secretary of State. Also register with the Department of Revenue for a Unified Business Identifier (UBI).

    Official government source

    $180 (LLC filing fee) + $19 UBI registration2–5 business days

City of Seattle / King County

2 stops

  1. City of Seattle Business License Tax Certificate

    All businesses operating in Seattle must obtain a Business License Tax Certificate from the Seattle Office of Housing and Finance. The annual fee is based on total annual income. Plumbing contractors must list their Washington State contractor registration number.

    Official government source

    $110/year (base fee for businesses under $20,000 revenue; higher for larger businesses)1–5 days (online application)

  2. Seattle Department of Construction and Inspections — Contractor Verification

    Plumbing contractors must have their Washington State plumber license and contractor registration verified with the Seattle Department of Construction and Inspections (SDCI) before pulling permits. No separate city plumbing contractor exam is required; the state license and registration are sufficient.

    Official government source

    No additional fee1–3 days

Terminus

Open for business — est. $800–$2,500 · 6–10 weeks to obtain all licenses and permits

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Official Sources

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