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 Hawaii, the written lease agreement is indeed a crucial document outlining the rights of residential tenants and the responsibilities of landlords. Tenants are encouraged to thoroughly review and understand the lease before signing, as it provides more legal protection than an oral agreement. Regarding late fees, Hawaii's landlord-tenant laws stipulate that any late fees must be reasonable and are governed by the terms set forth in the lease agreement. Hawaii Revised Statutes §521-21(d) states that any charge or fee, including late fees, must be agreed upon in advance and cannot be unconscionable. The law does not specify a maximum amount for late fees, but they must not be punitive and should reflect a fair estimate of the damages the landlord incurs due to late payment. Additionally, the concept of an implied duty of good faith and fair dealing is recognized in Hawaii's contract law, which means that landlords are expected to act fairly and not impose late fees in an unreasonable or excessive manner. For instance, charging a late fee for rent that is only an hour late without a clear stipulation in the lease that time is of the essence would likely be seen as a breach of this duty.