What the law says
California's Business and Professions Code section 7030.5 requires a licensed contractor's license number on all construction contracts, subcontracts and calls for bid, and in all forms of advertising. CSLB's Advertising Guidelines brochure lists the forms advertising can take: newspapers and radio, business cards, vehicle lettering, brochures, directories, contract proposals, and "any website or post that solicits business on the Internet."
In a September 2020 bulletin (#20-21), CSLB reminded contractors to put their license number on all commercial vehicles and advertisements, and said that "includes online sales postings and websites." The bulletin cites Business and Professions Code sections 7027, 7029.5 and 7030.5 and California Code of Regulations section 861.
What happens if it's missing
CSLB's brochure puts the civil penalty for leaving the license number off at $100 to $1,000 for a first offense. The 2020 bulletin gives a wider range of $100 to $5,000 for licensees who break the advertising laws in general. Either way, a missing number is an easy violation to avoid.
There is a practical reason too. Homeowners can check any California license with CSLB's free license lookup, and a number on your site makes that check take seconds.
Where to put it on your website
The rule says the number must be in the advertising. It doesn't set a size or position for websites, so aim for places visitors actually see:
- Near the top of the home page, close to your business name.
- In the footer of every page, so it appears whatever page someone lands on from a search.
- On your contact or quote page, next to your phone number.
- With your classification, for example "Lic. #1234567 · C-36 Plumbing", so homeowners know what work you're licensed for.
Use the business name that appears on your license. It lets homeowners match your site to your record in CSLB's lookup.
Your website isn't the only place this applies. CSLB's definition covers directories and any post that solicits business online, so add your number to your Google Business Profile, Yelp page and social media profiles wherever the platform gives you room.
Other advertising rules your website has to follow
The same CSLB guidelines include a few rules that catch people out online:
- Advertise only within your classification. A C-29 Masonry contractor can't advertise electrical work without a C-10 license. Licensed Class A and Class B contractors can advertise as general contractors.
- Don't advertise that you're bonded. CSLB says the law prevents contractors from noting in advertising that they are bonded, because it could make consumers think bonding offers more protection than it does.
- No false or misleading claims. Using false, misleading or deceptive advertising to win home improvement work is a misdemeanor. Reviews, photos and credentials on your site should be genuine and your own.
How ObraUp handles it
Every ObraUp design shows your license number and classification where homeowners look for them. When you start, we look up your license in public California license data, so the number and classification on your site come from your state record. You approve all content before your site goes live.
ObraUp builds websites. We don't give legal advice. For questions about your own situation, check CSLB's guidelines or ask a licensing attorney.
Questions people ask
Do I need my license number on Facebook, Yelp and Google?
CSLB's definition of advertising includes directories and "any website or post that solicits business on the Internet." Add your number to these profiles wherever the platform lets you, such as the business description.
Does the license number need to be a certain size on a website?
CSLB sets sizes for vehicle lettering (at least 72-point type or ¾ inch letters for most contractors) but its Advertising Guidelines don't give a size for websites. Make it easy to read.
Can my website say I'm insured?
CSLB's guidelines bar advertising that you're bonded, not that you're insured. Any insurance claim has to be true. ObraUp only shows an insurance amount you've verified with a current certificate.
Where can homeowners check my license?
On CSLB's website, using its free license lookup. Homeowners can search by license number, business name or personal name.
Sources
- CSLB, Advertising Guidelines for Contractors (checked October 13, 2026)
- CSLB bulletin #20-21, September 17, 2020: Include License Number on Vehicles and Advertisements (checked October 13, 2026)