How to Start a Plumbing Business in Washington: L&I Plumbing Contractor License, $148.10 Fee and $6,000 Bond

If you plan to do plumbing work for pay in Washington, you need a plumbing contractor license from the Department of Labor & Industries (L&I). Since January 1, 2021, RCW 18.106.020 requires a chapter 18.106 RCW plumbing contractor license. Registration under chapter 18.27 RCW is no longer enough by itself for plumbing work, and that is the mistake we see most often from new owners. This guide walks through the steps in the order you should take them, with the figures we verified and clear notes on where you should confirm a number directly with the agency.

What You Need Before You Start

Gather these items before you open any state website. Most applications stall because one of them is missing.

• A business name and a decision on structure: sole proprietorship, LLC, or corporation
• A physical street address in Washington for your registered agent (PO boxes and private mailbox addresses are not accepted)
• An email address for your registered agent
• A full-time journey or specialty plumber to designate on your license
• A $6,000 surety bond (up to $18,000 if residential judgments apply)
• Liability insurance that names L&I as certificate holder
• Funds for the state fees, which include $148.10 for the license, $180 for an LLC Certificate of Formation, $50 for the Business License Application, and $5 for each trade name

Step 1: Pick Your Structure and Check the Name

Your structure determines which filings you make. An LLC or corporation files with the Washington Secretary of State, Corporations and Charities Division, through the Corporations and Charities Filing System (CCFS). Sole proprietors and general partnerships do not file with the Secretary of State at all. Their first state filing is the Business License Application through the Department of Revenue.

If you form an LLC, the name must include Limited Liability Company, Limited Liability Co., L.L.C., or LLC under RCW 23.95.305. It must also be distinguishable from every other business name on record. Names containing bank, banking, banker, trust, cooperative, or certain combinations of building, savings, loan, home, association, and society are not allowed. If you need time to finalize the name, you can reserve it for 180 days for $30.

Next, file the Certificate of Formation with Initial Report. The filing fee is $180. Expedited service is $100 per business entity and is generally processed within three business days. The Secretary of State currently charges the $100 expedited rate for front-counter same-day requests received before 3:30 p.m., and the fee schedule lists a $150 same-day fee that it says it will announce 30 days in advance on its website before implementing. Confirm current rates on the Corporations and Charities Division page before you file.

Step 2: Name a Registered Agent

Every business must designate a registered agent in Washington under RCW 23.95.415. The agent can be commercial, registered with the Secretary of State, or noncommercial. The agent must consent to serve, supply an email address, and maintain a physical street address in Washington. Pick an agent who will be available during business hours, because the agent receives legal notices on your behalf. There is no fee to change the registered agent or the registered office later, so this is a low-stakes decision you can revisit.

Step 3: Get Your Plumbing Contractor License From L&I

This is the step that defines a plumbing business in Washington. You apply to L&I for a chapter 18.106 RCW plumbing contractor license. Based on the verified fee schedule, the license costs $148.10 per two-year issuance or renewal. Before you submit, you must meet these requirements:

• Designate a plumber. The license must have a full-time journey or specialty plumber designated to it. If you later replace that plumber, the change fee is $53.20.
• Post a bond. The bond is $6,000. After residential judgments, the required bond can rise to as much as $18,000.
• Carry insurance. Your liability insurance must name L&I as certificate holder. Confirm the minimum coverage amounts with L&I before you buy a policy, because the amounts are not listed in this guide.

If your license lapses, reinstatement costs $74.00 under WAC 296-400A-045. Keep your renewal date on a calendar, because the license runs on a two-year cycle. Application processing times are set by L&I, so confirm current timelines at lni.wa.gov rather than planning around a number from another source.

Step 4: Register With the Business Licensing Service

Once your entity exists with the Secretary of State, or immediately if you are a sole proprietor, register with the Department of Revenue's Business Licensing Service (BLS) through the Business License Application. One application covers the state business license, your Unified Business Identifier (UBI) number, trade names, and any city, county, or state endorsements.

You are required to register if any of the following apply: you operate under a name other than your full legal name, you plan to hire employees within 90 days, you sell anything subject to sales tax, your gross income is $12,000 or more per year, you owe a tax or fee to the Department of Revenue, or you need city, county, or state endorsements. Many plumbing businesses meet at least one of these tests on day one. The processing fee is $50 to open a business, plus separate endorsement fees. If you need a trade name, the registration is $5 per name, and it is filed with the Department of Revenue, not the Secretary of State or the county.

Expect the BLS timeline to vary. Online applications take about 10 business days, and two to three weeks longer when city or state endorsements need approval. Mailed applications can take up to six weeks. Plan your start date around the slowest endorsement you need.

Step 5: Confirm Local Permits and City Requirements

Washington has 39 counties and 281 incorporated places, and local requirements add a second layer to the state process. Cities and counties must verify your state plumbing contractor license before they issue a permit, so an active license is the key to pulling permits anywhere in the state. Permit fees are set locally, so check your city or county building department before you bid a job. Ask whether a local business license or endorsement applies in your jurisdiction.

You should also plan for local business taxes. About 54 cities levy their own business and occupation (B&O) tax, which the Department of Revenue does not administer. If you work in one of these cities, confirm the local rate and filing schedule directly with the city's finance or tax office.

Step 6: Understand Your Tax Obligations

Washington does not levy a corporate income tax or a personal income tax on wages. Instead, most businesses pay the state B&O tax, which is a gross receipts tax. It has more than 50 activity classifications and allows no deduction for labor, materials, or other costs. Your plumbing revenue may fall under a classification that differs from your supplies or service revenue, so confirm the correct classification with the Department of Revenue at dor.wa.gov before your first filing. The state sales tax rate is 6.5%. Whether a given charge is subject to sales tax depends on how you bill it, so ask the Department of Revenue or a CPA to review your invoice format.

Common Mistakes to Avoid

• Treating registration as enough. Since 2021, plumbing work requires the chapter 18.106 RCW license. A chapter 18.27 registration alone does not authorize plumbing contracting.
• Advertising before you are licensed. Advertising plumbing services without the license is a violation. Contractor infractions run $500 for a first offense, $1,000 for a second, $2,000 for a third, $4,000 for a fourth, and up to $5,000 after that. Each day and each job site is counted separately, so one ad left running for a month can produce a large total.
• Hiring certified plumbers as contractors. Certified plumbers may not work for an unlicensed contractor except as employees. Check your crew's status before you assign work.
• Using a PO box for the registered agent. The address must be a physical street address in Washington.
• Missing the annual report. An LLC or corporation must file its annual report, which costs $70, by the last day of the month in which it was formed or registered. It can be filed up to 180 days early. A late filing adds a delinquency fee, for a total of $95.
• Letting the bond or insurance lapse. Your license depends on both staying current, so track their renewal dates alongside the license.
• Skipping the local check. A state license does not replace a city or county permit or a local B&O filing.

What to Expect on Timing and Results

A typical path for a new LLC in Washington may look like this: a few days to form the entity, a few weeks for the business license and endorsements, and additional time for L&I to process your contractor application and bond. Some owners are able to move faster by filing expedited Secretary of State service and submitting clean, complete applications, while others find that a missing bond or insurance certificate adds weeks. Results depend on your structure, your jurisdiction, and how quickly each agency responds, so treat these timelines as planning estimates rather than guarantees.

A well-organized setup can help you avoid the most common delays. Keep copies of every filing, track each renewal date, and confirm each fee on the official agency page before you pay.

Next Steps and Professional Help

Start with the Secretary of State filing if you are forming an entity, then move to the Business License Application, then the L&I plumbing contractor license. For free help with the business plan, financing, or recordkeeping, the Washington Small Business Development Center offers advising. If your situation involves multiple owners, a mix of residential and commercial work, or a bond claim, consult a qualified attorney and a CPA before you commit.

Disclaimer

This article is informational content, not legal or tax advice. Fees, thresholds, and processing times can change. Confirm every figure with the responsible agency before you file, and consult a qualified attorney or CPA about your specific structure, tax position, and licensing needs.