Most residential landlords require tenants to pay a security deposit to cover any repairs needed when the tenant moves out, or to cover the tenant’s failure to pay the last month's rent.

Laws vary from state to state, but many states have statutes that provide the maximum amount of security deposit a landlord may require for a residential lease and the costs for which the landlord may use the security deposit (cleaning, repairs, unpaid rent) following termination of the lease.

These laws also provide a specific deadline (often 30-60 days) for the landlord to return the tenant’s security deposit following termination of the lease—after deducting any amount properly withheld, as allowed by law.

In Massachusetts, the security deposit laws are governed by the Massachusetts General Laws Chapter 186, Section 15B. Landlords can require a security deposit from tenants, but it must not exceed the amount of one month's rent. The security deposit can be used for covering the cost of repairs for damage caused by the tenant beyond normal wear and tear, unpaid rent, and unpaid utility bills. Landlords are required to hold security deposits in a separate, interest-bearing account in Massachusetts and provide the tenant with a receipt detailing the bank's name and account number. Upon termination of the lease, the landlord must return the security deposit or provide a detailed statement of damages within 30 days. If the landlord fails to comply with these regulations, they may be liable to pay the tenant three times the amount of the security deposit, plus interest, court costs, and attorney's fees.