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How do you check a license for plumbing in California?

For plumbing work in California, start with the Contractors State License Board (CSLB) and its C-36 classification. The public lookup accepts a contractor license number or business name, with a separate person-name search for associated licenses. The C-36 scope covers water supply and fluid-waste disposal.

Source: CSLB public lookup and search tips, read 5 November 2026.
Source: CSLB C-36 classification, read 5 November 2026.
Source: Contractors State License Board agency scope, read 5 November 2026.

The license lookup is yours to run on the state's site.

InstaBids is an AI-run marketplace for homeowners and property managers: describe a home job once, by chat or through your own AI assistant, add photos, and get multiple written quotes on the same scope, compared apples to apples, with no phone calls or home visits before you pick.

By InstaBids editorial team with AI research agents. Sources last read: 5 November 2026

InstaBids assistantAI · builds your written scope with you

What plumbing job do you need done in California? Describe it once to start your written scope.

Start from a common job
You choose who gets your number
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  1. Describe it onceBy chat, or through your own AI assistant, and add photos.
  2. Post it and send itContractors bid in writing on that scope.
  3. Compare line by lineEvery quote is written against the same scope.
  4. You chooseContact details stay hidden until you pick and they confirm.
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Hand any of these to your assistant and it can help you write this job's request; you send the request yourself. What you type in the job box above goes into the prompt these buttons carry. The connector asks you to sign in to your InstaBids account the first time.

  • MCP connector URLhttps://instabids.ai/api/agent/mcp
  • Agent API (OpenAPI)https://instabids.ai/openapi.json
  • Start-request linkhttps://instabids.ai/intake?from=licence-california--plumbing&utm_campaign=licence&page_type=licence&job=plumbing&place=california&utm_source=us&utm_medium=page
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Key facts

How do you look up a plumber in California?

Use CSLB's public search by contractor license number or business name; its separate person-name search finds associated licenses. Open the official lookup, rather than the application-status service.

Source: CSLB public lookup and search tips, read 5 November 2026.

CSLB's number-entry guidance says: "A California contractor license number doesn't contain alphabetic characters. Each contractor's plastic pocket license will show the respective license number. Begin entry of your license number at the left position and don't exceed 8 digits in the license number." Read the status exactly as the record shows it. Source: CSLB lookup, read 5 November 2026.

Source: CSLB public lookup and search tips, read 5 November 2026.

Keep your optional CSLB number search separate from the written request on InstaBids, where you describe the fixture, access and work needed.

What work does the C-36 classification cover?

C-36 is the plumbing classification shown on CSLB's scope page. The CSLB classification description, under California Code of Regulations, Title 16, Division 8, Article 3, states: "A plumbing contractor provides a means for a supply of safe water, ample in volume and of suitable temperature for the purpose intended and the proper disposal of fluid waste from the premises in all structures and fixed works." Read the full description for its listed categories of work. Source: CSLB C-36 page, read 5 November 2026.

Source: CSLB C-36 classification, read 5 November 2026.

Use the C-36 scope as an optional reference while describing water supply or waste-disposal work and equipment in your written request on InstaBids.

What if a business-name search finds no license?

Try CSLB's shorter-name search instructions before drawing a conclusion from an empty business-name search. The official search tips say: "Type only the first 10 to 15 letters of the business name. If you do not find the license, type the business name again with 1 or 2 fewer characters." These are entry tips, rather than an exemption or a verdict about the business. Source: CSLB lookup, read 5 November 2026.

Source: CSLB public lookup and search tips, read 5 November 2026.

After an optional CSLB business-name search, focus your written request on InstaBids on the leak, replacement or installation and the access it needs.

What should a plumbing home-improvement contract say?

CSLB's contract guidance calls for written permit responsibility and a completion date. Its contract page says: "The contract needs written direction as to who will get the necessary permits, and must provide a date of completion." Source: CSLB contract guidance, read 5 November 2026.

Source: CSLB home-improvement contract guidance, read 5 November 2026.

The same CSLB page adds: "Make sure the contract includes details like cleanup and removal of debris and materials, and special requests like saving lumber for firewood." For a plumbing request, describe any cleanup or removal you want included so it can appear in the written scope. Source: CSLB contract guidance, read 5 November 2026.

Source: CSLB home-improvement contract guidance, read 5 November 2026.

Use CSLB contract topics to outline permit responsibility, a proposed completion date and cleanup when composing the written scope of your request on InstaBids.

How do you file a complaint with CSLB?

Start at CSLB's page for filing complaints and follow its homeowner complaint-form link. The filing page explains: "Use this form if you are a homeowner, other contractor, subcontractor, or employee who wants to file a complaint against a contractor." Source: CSLB complaint guidance, read 5 November 2026.

Source: CSLB complaint guidance, read 5 November 2026.

Before completing that form, note the same page's preparation question: "CSLB will ask if you have formally notified your contractor of your concerns with the project." Keep that agency process separate from requesting bids for other work. Source: CSLB complaint guidance, read 5 November 2026.

Source: CSLB complaint guidance, read 5 November 2026.

Treat the CSLB complaint form as a separate agency process; in a new written request on InstaBids, describe remaining work and existing conditions.

Where does InstaBids fit in?

One point about InstaBids follows. There is no cost to see a request or bid.

Describe the job once on InstaBids, and contractors can bid in writing on one written scope. Homeowners pay InstaBids nothing.

Homeowners anywhere in the US can post a job; once you send it, InstaBids finds contractors to bid on it.

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