The most important source of information about a residential tenant’s rights and a landlord’s responsibilities is the written lease agreement. Some landlords prefer oral agreements, but it is more common for them to require the tenant's signature on a written lease—and a written lease protects the tenant more than an oral agreement. Be sure to read the lease carefully before you sign it.

A residential landlord’s ability to charge late fees generally depends on the specific language in the written lease agreement; the state’s landlord-tenant laws that may limit the amount of late fees the landlord can charge and the circumstances in which they can be charged; and the state's contract law.

Contract law in most states recognizes an implied duty of good faith and fair dealing between parties to a contract, and a residential landlord who charges late fees because the tenant is an hour late paying the rent may be in breach of the landlord’s implied duty of good faith and fair dealing—unless, for example, the lease agreement specifies an hour (12:00 p.m.) of the day by which rent is due and states that time is of the essence.

In Massachusetts, the written lease agreement is indeed a crucial document outlining the rights of residential tenants and the responsibilities of landlords. While oral agreements are legally binding, a written lease provides clearer protection for both parties. Tenants should thoroughly review and understand the lease before signing. Regarding late fees, Massachusetts law stipulates that landlords cannot charge a late fee until rent is 30 days overdue. This is outlined in Massachusetts General Laws Chapter 186, Section 15B. Additionally, the state upholds the implied covenant of good faith and fair dealing in contracts, which means that landlords must act fairly and may not impose late fees in an unreasonable or punitive manner. For instance, charging a late fee for rent that is only an hour late without a specific provision in the lease stating such a strict deadline would likely be considered a breach of this duty. It is important for tenants to be aware of these legal protections and for landlords to ensure their lease agreements and practices comply with state regulations.