Deposit vs. prepaid last month’s rent
Usually not, unless the money was specifically designated as last month's rent. A general security deposit and prepaid "last month's rent" are treated differently, and assuming you can skip your final rent payment using your deposit can get you into trouble.
If you paid a security deposit, it is meant to cover things like damage and unpaid rent after you leave — not to automatically serve as your last month's payment. Refusing to pay your final month's rent and telling the landlord to "use the deposit" can leave you owing rent and risking problems, even though you will still be entitled to the deposit's return afterward, minus lawful deductions.
The situation is different if part of your move-in money was clearly labeled and paid as "last month's rent." In that case, it may be intended to cover that final month.
Because the labels and your agreement matter, it is worth checking what you actually paid and how it was designated. If you are unsure whether you can apply money toward your last month's rent, a free, confidential review can help you avoid a costly mistake.
This is general information about California tenant rights, not legal advice. Every situation is different.