Free guide · King County, WA

Your first 30 days with a WA food trailer: King County

Last checked Nov 2026 against the official L&I, Public Health – Seattle & King County, Department of Revenue, and City of Seattle pages linked below.

Days 1–3: Find out what you actually bought

Walk around the trailer and look for the L&I insignia. L&I tells buyers to make sure a unit "is inspected and approved for use in Washington, and has our insignia attached" (L&I).

The tag lists the approved plan number, the electrical service (amps/volts), the number of plumbing fixtures, and whether the unit was plan exempt. Take a clear photo. Public Health asks for a photo of the L&I sticker with your application (King County).

Two things that catch new owners:

• A used trailer still needs its own county approval. King County says owners must submit plans for review before construction, remodeling, or a change of ownership. Operating permits are not transferable to a new owner (King County).
• Check it's really a "food truck or trailer" to L&I. That means people work inside, customers stay outside, it's licensed as a vehicle, it's no more than 8.5 feet wide, and it has 120 V or more electrical, water/drain, or propane piping. If customers can go inside, it may be a commercial coach instead (L&I).

Week 1: State business license and UBI

File a Washington Business License Application with the Department of Revenue. You need one if, among other things, you collect sales tax, use a name other than your legal name, plan to hire within 90 days, or gross $12,000 a year or more (DOR).

• If you're forming an LLC or corporation, file with the Secretary of State first (DOR).
• Online applications take about 10 business days. City or state endorsements can add 2–3 weeks. Mailed applications can take up to six weeks (DOR).
• Processing fee to open a business is $50, plus any endorsement fees (DOR fees).
• You get a UBI number. You'll use it on almost every form after this.

Also start your food worker cards now. Every employee of a food business needs a Washington food worker card. It's $10, and you can take the class and test online (King County).

Week 1–2: L&I insignia (plans or inspection only)

This is usually where it stalls, so start it early. Public Health will not approve your pre-operational inspection and permit until L&I has approved the truck or trailer. You can submit the county application before L&I approval, though (Seattle OED).

Do you need to submit plans to L&I?

You need plans approved before inspection if you have any of these (L&I):

• Commercial cooking equipment like a fryer, stove, or oven that needs a hood (espresso machines and small plug-in appliances don't count)
• Wood or charcoal cooking equipment
• A propane or other fuel gas piping system
• Electrical over 50 amps, over 240 volts, or more than 5 circuits
• Solar or other alternate energy
• A bathroom or plumbing for bodily waste
• Any single piece of equipment over 500 pounds

Before any inspection, go through L&I's pre-inspection checklist (F622-072-000). L&I charges for the inspection even if the trailer isn't ready, and charges again for extra trips (L&I). It's cheaper to fix on paper than at inspection.

L&I contact: FAS1@Lni.wa.gov, 1-800-705-1411, Option 3.

Week 2–3: Lock in a commissary and a restroom

You can't file your county plan review without these two signed agreements. Line them up while L&I is working.

Commissary

• Food businesses must operate out of an approved facility inside King County. The commissary needs at least a 3-compartment sink, a mop sink for dumping wastewater, and a hand sink (Use of Commissary Agreement).
• Mobile units must return to the commissary daily for storage and cleaning, unless Public Health approves written alternative procedures in advance (Plan Review Guide).
• Cutting, chopping, and slicing aren't allowed on the mobile unit. That prep happens at the commissary (Plan Review Guide).
• Wastewater gets dumped at the commissary or an approved site, never on the ground or street. If you use an RV dump, attach the site address and a permission letter (Plan Review Guide).
• Find approved kitchens on the county's commissary map. It's on you to contact the kitchen and confirm it fits your menu.

Restroom

• Employees need a restroom within 500 feet. If you stay at any one location more than an hour, you need a signed Use of Restroom Agreement for that stop, kept on the trailer (Plan Review Guide).
• If you offer seating, customers need a plumbed restroom within 500 feet (Plan Review Guide).

Week 3–4: Public Health plan review

More detail on the county side: King County health permit for food trucks: steps and 2026 fees.

Apply online in the Public Health Permit Center. You must pay the fee to finish submitting (King County). Start with the Mobile Food Unit Plan Review Guide. Incomplete plans are not accepted for review.

What goes in the package

• Plan review application and cover sheet
• Trailer floor plans with dimensions, make and model of each piece of equipment, plus photos inside and out and of the L&I sticker
• Water system drawing: fresh and waste tanks, water heater, pump, hand sink, 3-compartment sink
• Signed commissary agreement and a drawing of the commissary
• Signed restroom agreement and the site or route form
• Detailed menu and a food prep flow chart (what happens at the commissary vs. on the trailer)
• Mobile Operational Questionnaire

Source: Plan Review Guide, King County plan review page.

Water details reviewers check

• The hand sink needs warm water under pressure (100–120°F) and at least 5 gallons of fresh water just for hand washing.
• The waste tank must hold at least 15% more than the fresh tank.
• Occupied units need a 3-compartment sink with hot and cold running water.
• Tanks and tubing must be food grade. Hoses need vacuum breakers.

Source: Plan Review Guide, Appendix A.

Plan review questions: 206-263-7833, ehfoodandfacilitiesplan@kingcounty.gov.

Fire permit (propane, charcoal, wood, fryers)

King County's guide says fire department approval and a permit are required if you use liquid propane, charcoal, wood, or oil frying equipment (Plan Review Guide).

• A permit is generally required from each jurisdiction you operate in. Seattle and other participating fire departments accept one shared Washington State Association of Fire Marshals (WSAFM) checklist inspection each year. With proof of that inspection, most jurisdictions, Seattle included, give a discounted permit (Seattle Fire).
• If you have fuel gas piping, Seattle Fire calls for an annual fuel gas piping inspection under the 2021 International Fire Code 319.10.3 (Seattle Fire).
• Outside Seattle, call the fire department or fire marshal for each city you plan to work in before your first event.

Selling in Seattle: the extras

• City business license. Anyone doing business in Seattle needs a Seattle business license tax certificate, renewed every year by Dec. 31. Apply on FileLocal. The 2026 fee is $73 under $20,000 in Seattle taxable revenue and $147 for $20,000–$499,999 (Seattle City Finance).
• Seattle Fire permit. You need it to cook with propane, solid fuel, open flame, or charcoal. 8206-TRK includes an SFD inspection, and 8206-RGL is the lower-priced option when a partner jurisdiction already inspected you. Both are good for 12 months (Seattle OED). SFD inspects on Wednesday mornings (Seattle Fire).
• Street vending (curb, sidewalk, plaza). You need an SDOT Street Use vending permit. You'll need your Seattle business license, a health permit, a fire permit if you cook with propane, photos showing your plate, and a site plan (SDOT).
• Timing matters right now. The SDOT vending year runs Feb 1 to Jan 31. Unrenewed locations open for applications Dec 1, and SDOT holds a lottery for them the first week of January (SDOT).
• Private lots in Seattle may need a permit from SDCI. Check with the city before you set up (Seattle OED).
• No alcohol sales to the public from a mobile unit. A liquor caterer license only covers private events (Seattle OED).

Outside Seattle, other cities may need their own business license, and parking rules on public and private property differ city to city (Seattle OED). L&I also warns that some local building departments may not allow food trucks or trailers at all (L&I).

After day 30: getting to opening day

1. Answer reviewer questions fast. Watch your email and the Permit Center. Once your plans are stamped, the reviewer emails your approval letter.
2. Apply to operate. Use the approval letter to file the operating permit application in the Permit Center. Submit it once and wait for the emailed invoice. The operating fee is separate from the plan review fee.
3. Pass L&I inspection. Once your L&I plans are approved, you get an inspection request form. Seattle OED says inspections average about 2–3 weeks from request (Seattle OED).
4. Book the pre-operational inspection. Contact your plan reviewer at least 1 week ahead and send in the pre-operational checklist. Opening without this inspection can mean closure and fees, including 50% of the annual permit fee.
5. Keep the approved plans on the trailer. Inspectors will ask to see them. Changes to the unit, menu, prep, or commissary without written approval can get you closed.

Sources: King County mobile permit page, Plan Review Guide.

Fee cheat sheet (as posted, Nov 2026)