It is illegal for contractors to work without a license in California if their work exceeds $500 (including labor and materials). Contractors performing any kind of construction or home improvement work where the total cost exceeds this threshold must hold an active license issued by the Contractors State License Board (CSLB). The CSLB regulates contractors across various trades such as plumbing, electrical, landscaping, and general construction. Obtaining a license requires meeting specific requirements such as demonstrating experience and passing examinations related to trade knowledge and business practices. Unlicensed contractors are subject to penalties including fines and potential legal action since licensing ensures that contractors adhere to certain standards and consumer protections while preventing unqualified individuals from engaging in potentially unsafe or subpar construction work.