Legal Question in Construction Law in California

There is nothing you can do. You have violated the contractor's license law. You have done construction work without a license. Although it may be unlikely that you will be prosecuted, that is a crime. It also means the property owner not only does not legally owe you the balance, they have the right to demand you give them back what they already paid you, and they can sue you to get it back. The law is very clear. If you don't have a license no one owes you anything for construction work you do, no matter how much the work is worth or cost you. It makes zero difference whether you are honest about not having the license or not. No license, no right to be paid for the work. Period. The only exception is handyman work for less than $500.