As a general rule, a tenant is bound to the length of the lease unless the landlord significantly breaks the law or violates its terms -- for example, by failing to make necessary repairs, or by failing to comply with an important lease clause. A few states have laws that allow tenants to break a lease because of health problems or a job relocation that requires a permanent move. Federal law and many similar state laws allow tenants who enter active military service and related government positions to terminate a lease early.
A tenant who breaks a lease without good cause will be responsible for the remaining rent due under the lease term. In most states, however, a landlord has a legal duty to use reasonable efforts to try to find a new tenant -- no matter what the tenant's reason for leaving -- rather than charge the tenant for the total remaining rent due under the lease.
A landlord may legally terminate a lease if a tenant significantly violates its terms or the law -- for example, by paying the rent late, keeping a dog in violation of a no-pets clause in the lease, substantially damaging the property, or participating in illegal activities on or near the premises, such as selling drugs.
A landlord must first send the tenant a notice stating that the tenancy has been terminated. State laws set out very detailed requirements as to how a landlord must write and deliver (serve) a termination notice. Depending on what the tenant has done wrong, the termination notice may state that the tenancy is over and warn the tenant that he or she must vacate the premises or face an eviction lawsuit. Or, the notice may give the tenant a few days to clean up his or her act -- for example, to pay the rent, or to find a new home for the dog. For details on rent-related terminations, see your state's rent rules. For other types of terminations, see your state laws on unconditional quit terminations.
If the tenant fixes the problem or leaves as directed, no one goes to court. If a tenant doesn't comply with the termination notice, the landlord can file a lawsuit to evict the tenant. For more information, see Nolo's article How Evictions Work: Rules for Landlords and Property Managers.
For a comprehensive legal and practical guide for landlords, see Every Landlord's Legal Guide, by Marcia Stewart, Ralph Warner, and Janet Portman (Nolo).
Landlords may make deductions from a tenant's security deposit, provided they do it correctly and for an allowable reason. Many states require landlords to provide a written itemized accounting of deductions for unpaid rent and for repairs for damages and necessary cleaning that exceed normal wear and tear, together with payment for any deposit balance.
The deadlines vary from state to state, but landlords usually have a set amount of time in which to return deposits, usually 14 to 30 days after the tenant moves out -- either voluntarily or by eviction. (See Nolo's Chart: Deadline for Returning Security Deposits, State-by-State.)
(If your landlord is withholding your security deposit, see Nolo's article Get Your Security Deposit Back.)