A security deposit is an amount of money given by the tenant to the landlord to ensure that reimbursement is available for any damage done to the premises by the tenant. Some leases require additional deposits for pets or waterbeds. State laws require the return of the security deposit within a certain period of time. If the entire security deposit is not returned, the landlord should provide the tenant with a written explanation regarding any deductions made from the security deposit. Some states have laws with steep financial penalties for landlords that fail to return the security deposit within the amount of time allowed by law. A security deposit typically cannot be credited toward the payment of the final month’s rent. Some state laws require the landlord to keep the security deposit in a separate interest bearing account.