(KRON) — An undercover sting operation busted 13 people working as contractors in California’s South Bay without the proper license, the Contractors State License Board (CSLB) said. CSLB worked with the Santa Clara County District Attorney’s Office and the California Department of Insurance on the operation.

According to CSLB, the unlicensed contractors submitted bids as high as $45,000. A contractor’s license is required for anything that costs more than $500 in California.

The contractors also asked for down payments that CSLB described as “excessive.” By California law, down payments must be 10 percent of the total project cost and cannot exceed $1,000.

The unlicensed contractors may also face charges for advertising their services without the necessary license.

“CSLB is dedicated to protecting homeowners from the risks associated with unlicensed contractors,” said CSLB Registrar David Fogt. “We are committed to continually educating consumers about the importance of hiring licensed contractors. We strongly urge California homeowners to verify a contractor’s license before starting any construction project.”

For the lack of license, the contractors face fines of up to $15,000 and up to six months of jail time. Repeat offenders will be hit harder. For the oversized down payments, punishment includes fines up to $5,000 and/or a year in county jail.

CSLB made a similar bust in the South Bay last month, citing 14 unlicensed contractors in Campbell.