When was my final paycheck actually due under California law?

The exact deadline depends specifically on how your employment ended. If you were fired or laid off, California law requires your final paycheck immediately, on your last day of work, delivered at the place of termination. If you quit and gave your employer at least 72 hours advance notice, it's due on your last day as well. If you quit without giving that notice, your employer has 72 hours from your departure to pay you.

These specific rules come from Labor Code sections 201 and 202. A few categories of work, including seasonal employment, certain entertainment industry roles, and oil-drilling positions, have their own separate rules that differ from this general framework, so it's worth checking whether your job falls into one of those categories.