CSLB License Lookup: How to Check Any California Contractor

Why a License Number Alone Isn't Enough

A license number printed on a bid tells you almost nothing. The Contractors State License Board itself warns that seeing a license number doesn't necessarily mean the license is valid — the status behind that number is what matters, and only CSLB can confirm it.

This blind spot carries real weight in Altadena right now. Homeowners planning ADUs, garage conversions, or Eaton Fire rebuilds are signing large contracts quickly, and unlicensed contracting is a misdemeanor under California Business and Professions Code 7028 — yet unlicensed operators still bid on fire rebuilds with tempting low prices. CSLB's own guidance is blunt: the risks of financial and legal consequences outweigh any savings a lower bid seems to offer.

The protections you might assume exist are thinner than they look. Every licensed contractor files a $25,000 surety bond, but CSLB cautions that this bond is often not enough to cover multiple complaints or a project worth more than the bond's value — and bonds do not assure a contractor's competency. On a typical Altadena ADU or rebuild, $25,000 doesn't go far.

Workers' compensation is the sharper risk. If a contractor with employees lacks coverage, you can be financially liable for injuries on your own property. A workers' comp exemption on file is legitimate for a solo operator — but a red flag if a crew of three or more will be swinging hammers in your backyard.

The most common fraud pattern is subtler than "no license at all":

• The license number on the proposal belongs to a different business than the one named on the CSLB record — a name mismatch is the most common scam pattern in California.
• The classification doesn't match the job; a C-39 roofer, for example, cannot legally take on a full kitchen remodel or ADU build.
• The license is suspended, inactive, or expiring within 90 days — meaning the contractor cannot legally contract for new work.

The fix costs nothing. The free lookup at cslb.ca.gov takes about five minutes and surfaces the issues referrals rarely mention. At Altadena ADU Builder, we treat it as the first filter before any builder conversation — including vetting our featured builder, JMB Builders LLC (CSLB #1103479), whose license you can verify yourself in the same session. Before you sign anything, run the number.

The 3-Step CSLB Lookup, Start to Finish

The whole check takes about five minutes, it's free, and it surfaces the issues that referrals rarely mention. Here's the verified process, start to finish.

Step 1: Get the license number. California law requires contractors to display their CSLB license number on contracts, bids, and advertising, so it should be printed right on the proposal. As licensing experts put it, a contractor who can't or won't provide a number is an immediate cancellation — don't do business with them. And keep in mind CSLB's own warning: seeing a license number doesn't necessarily mean the license is valid, which is why steps 2 and 3 exist.

Step 2: Search the official tool. Go to the CSLB's "Check a License" page at cslb.ca.gov and search by the 4–8 digit license number, business name, or personnel name. A name search returns up to 25 matching current licenses with number, city, and status, according to this compliance guide. Prefer the phone? Call 800-321-2752 — CA.gov notes the best windows are Wednesday–Friday, 9:30–11:30 a.m. or 2–4 p.m.

Use the official site rather than third-party lookups, which contractor blogs advise against because they update slowly. If a number returns nothing at all, the license is expired, cancelled, inactive, or never issued — treat that as a stop sign.

Step 3: Read the detail page before signing. The result shows eight fields worth reviewing:

• Status — "Active" is the only acceptable status; suspended or expired means walk away
• Business information — the legal name must match the proposal; a mismatch is one of the most common scam patterns
• Classifications — for an ADU, garage conversion, or rebuild, you want a "B" General Building classification
• Bond — the required $25,000 surety bond must be on file, though CSLB cautions it's often insufficient and doesn't guarantee competency
• Workers' compensation — current coverage, or a legitimate exemption if it's truly a solo operator

Also scan personnel, license history, and any disciplinary or judgment disclosures. CSLB explicitly recommends reading its "Hiring a Contractor" guidance before signing anything.

You can see the process in action with any Altadena builder you're considering — for example, JMB Builders LLC, CSLB #1103479, an Altadena-based general contractor whose license and Eaton Fire rebuild work are documented on jmb-builders.com. At Altadena ADU Builder, we encourage every homeowner to run this same check, then pair it with references and reviews before committing. When you're ready to talk through whether your lot can support an ADU, our free feasibility consultation — with a cost quiz and concept render — is a good place to start.

How to Read the Results: Status, Classification, Bond, and Workers' Comp

Finding the license record is only half the job — the other half is knowing what the fields actually mean. Four things on the CSLB detail page must check out before you sign anything, and each one catches a different failure mode.

Status: "Active" is the only acceptable answer. Inactive, suspended, or expired means the contractor cannot legally contract for new work right now, and a suspended license means walking away until it's reinstated. CSLB suspends licenses for serious reasons: failure to maintain workers' comp, unpaid bond claims, unresolved citations, or non-compliance with a CSLB investigation. A suspended contractor cannot legally take jobs requiring a permit, using employees, or totaling $1,000 or more.

Business name: the proposal must match the CSLB record exactly. A name mismatch between the paperwork in your hand and the record on file is the most common scam pattern in California license fraud — someone borrowing a legitimate number that belongs to a different legal entity. CSLB also warns that "seeing a license number doesn't necessarily mean the license is valid," so verify the number yourself rather than trusting the printout. Ask to see the pocket license with photo ID to confirm the person matches the record.

Classification: for an ADU, look for a "B." A B General Building Contractor is licensed for projects involving two or more unrelated trades — ADUs, additions, full remodels. The classification must match the scope of work quoted; a C-39 roofer, for example, cannot legally take on a full kitchen remodel. For Altadena homeowners planning ADUs, garage conversions, or Eaton Fire rebuilds, a B classification (or the appropriate specialty C-class) is what you want to see.

Bond and workers' comp: confirm both are on file. Every licensed California contractor must carry a $25,000 surety bond, and workers' comp is required for any contractor with employees. The stakes are real:

• If a worker is hurt on your property and the contractor lacks coverage, you may be financially liable for the injury.
• A workers' comp exemption is valid for a solo operator — but a red flag if a crew of three or more will be on site.
• A missing or lapsed bond suspends the license automatically.

One caveat CSLB is explicit about: the bond is limited recourse, not insurance. It is "often not enough to cover multiple complaints" or a project worth more than the bond's value, and bonds "do not assure the financial or professional integrity or competency of a contractor." A clean record isn't proof of perfection, either — most consumer complaints never appear in the disciplinary section, so pair the lookup with references and reviews. When we at Altadena ADU Builder vet builders for this guide, the lookup is step one, never the only step.

Red Flags Checklist: When to Walk Away

A five-minute CSLB lookup can save you from a six-figure mistake — but only if you know what a dealbreaker looks like. Here's the checklist we use when vetting builders for our Altadena ADU guides: if any item below is true, stop and walk away.

• No license number provided. California law requires the number on all bids, contracts, and advertising. If a contractor can't or won't give you one, sources call it an immediate cancellation — unlicensed contracting is a misdemeanor under Business and Professions Code 7028.
• License not found in the system. A number that doesn't come up at cslb.ca.gov means the license is expired, cancelled, inactive, or never issued. Treat that as a stop sign until the contractor produces one that checks out.
• Suspension. The CSLB lookup shows why a license was suspended — commonly failure to maintain workers' comp, unpaid bond claims, unresolved citations, or noncompliance with an investigation. A suspended contractor cannot legally take jobs totaling $1,000 or more. Wait for reinstatement before signing anything.
• Expiration within 90 days. A license that lapses mid-project leaves you exposed. Only "Active" is acceptable.
• Classification mismatch. For an ADU, garage conversion, or whole-home remodel, you want a "B" General Building classification. A C-39 roofer cannot legally take on a full remodel, and unscrupulous contractors have been known to operate under a license for different work than they perform.
• Missing bond. Every licensed California contractor must have a $25,000 surety bond on file. A missing or lapsed bond suspends the license automatically.
• Workers' comp exemption with a crew. An exemption means no employees are claimed — legitimate for a solo operator, but a serious red flag if three or more people will be on your site. If a worker is injured on your property and there's no coverage, you may be financially liable.
• Unregistered salespeople. Anyone selling home improvement contracts must be registered with CSLB as a Home Improvement Salesperson. Ask for the registration card and photo ID.

One more name-related check: if the business name on the proposal doesn't match the CSLB record, that's one of the most common scam patterns in California license fraud. Ask to see the contractor's pocket license with photo ID to confirm the person matches the license.

Finally, know your down-payment protection: California caps the deposit at 10% of the contract price or $1,000, whichever is less, unless the contractor has a Blanket Performance and Payment Bond on file with CSLB — a protection held by only about two dozen licensees statewide. Any contractor demanding more upfront is either breaking the law or hasn't read it.

When you're comparing ADU builders in Altadena, run this checklist on every candidate. Our featured builder, JMB Builders LLC (CSLB #1103479), passes it — and you can verify that yourself in about five minutes. Want help vetting your shortlist? Request a free ADU feasibility consultation with a cost-quiz concept render from Altadena ADU Builder.

Note on links: I used the CSLB hiring page for the suspension/bond/down-payment claims. (One URL in the source list contained a typo I corrected to the canonical CSLB hiring page; the other source URLs were not needed for this section's claims.)

What the Lookup Can't Tell You — and How to Finish Vetting

A clean CSLB record tells you a contractor is legal to work in California. It does not tell you whether they'll answer your calls on Tuesday, honor the original budget, or show up for the punch list. As one licensing guide puts it, "a clean record is not proof of perfection" — most consumer complaints never appear in the disciplinary section at all.

The lookup also has structural limits. CSLB itself cautions that the required $25,000 surety bond "is often not enough to cover multiple complaints" and "does not assure the financial or professional integrity or competency of a contractor" (CSLB consumer guidance). Even the mandatory arbitration threshold sits at $25,000 or less for complaints, with a voluntary range up to $50,000 — modest protection on a six-figure ADU project.

So treat the lookup as step one, not the whole vetting process. To finish the job:

• Read Google and Yelp reviews for patterns — especially anything about change orders, delays, and communication.
• Check the contractor's Better Business Bureau profile for complaint volume and resolution behavior.
• Ask for 2–3 recent client references and call them, focusing on how the builder handled surprises.
• Verify insurance directly with the carrier, since fraudulent proof-of-coverage documents have occurred in the industry.

Here's what a complete picture looks like in practice. JMB Builders LLC (CSLB #1103479) is an Altadena-based licensed general contractor building ADUs, custom homes, and Eaton Fire rebuilds — you can confirm the license in the CSLB tool, and its projects and service areas are documented on jmb-builders.com. The lookup verifies the license; the portfolio and references verify the work. (Disclosure: JMB Builders is a paid featured builder on this site.)

If you're weighing whether a backyard ADU makes sense on your Altadena property, Altadena ADU Builder offers a free ADU feasibility consultation, including a cost-quiz concept render so you can see real numbers before you ever sign a contract.