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 Louisiana, the lease agreement is indeed a crucial document for outlining the rights and responsibilities of both residential tenants and landlords. While oral lease agreements are legally recognized, a written lease provides clearer protection for both parties and is strongly recommended. The lease should be read thoroughly before signing. Regarding late fees, Louisiana law allows landlords to charge them as specified in the lease agreement. However, the fees must be reasonable and not punitive. The state does not have a statutory limit on late fees, but they should reflect a fair estimate of the costs the landlord incurs due to late payment. Additionally, Louisiana recognizes the implied duty of good faith and fair dealing in contracts, which means that a landlord's actions, including the imposition of late fees, should be fair and not overly burdensome. If a lease specifies a particular time by which rent is due and emphasizes that time is of the essence, tenants should adhere to this requirement to avoid late fees. However, charging a late fee for rent that is only an hour late could potentially be seen as a breach of good faith, depending on the circumstances and the lease's provisions.