In California, the rules for power of attorney (POA) require that the document be in writing and signed by the principal, who must be mentally competent at the time of signing. The POA can either be durable, remaining in effect even if the principal becomes incapacitated, or non-durable, ceasing to be effective upon the principal's incapacity. It needs to be notarized or witnessed depending on its purposes; for instance, certain financial transactions might require notarization. Additionally, a POA can grant general authority across various decisions or specialized authority limited to specific tasks.