Limits on demanding more deposit
Generally, a landlord's ability to demand more deposit money during your tenancy is limited, and any total deposit still cannot exceed the legal cap that applies to your rental.
Because California caps security deposits — for most landlords, at one month's rent — a landlord cannot collect a total deposit above that limit, whether at move-in or later. If your existing deposit is already at the cap, there is generally no room to demand more.
Any change to the amount of money you must pay usually has to follow the proper rules for changing lease terms, including required notice, and cannot be used as a way to pressure or retaliate against you. A sudden demand for more deposit money after you complained about conditions, for example, could raise retaliation concerns.
So a landlord cannot simply decide to hold more of your money on a whim or beyond the legal limit. If your landlord is demanding additional deposit money during your tenancy and you are unsure whether it is allowed, a free, confidential review can help you understand your rights.
This is general information about California tenant rights, not legal advice. Every situation is different.