It is a common misconception that employees are entitled to three warnings before termination. No existing law stipulates a specific number of warnings.
California Labor Code section 2922 presumes that employment is at-will and can be terminated with no warning at all unless the parties have agreed otherwise. An agreement about the number of warnings issued can come from oral assurances, written contracts, employee handbooks, or can even be implied based on your practice of giving a certain number of warnings to other employees. Avoid any explicit or implied agreement requiring you to provide a certain number of warnings in all situations. Retain discretion to make disciplinary decisions based on the severity of the violation.