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 New Jersey, 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 protection than an oral agreement. Regarding late fees, New Jersey law allows landlords to charge them as specified in the lease agreement. However, the amount and conditions under which late fees can be imposed may be subject to state regulations. New Jersey's Anti-Eviction Act (N.J.S.A. 2A:18-61.1 et seq.) and the Truth in Renting Act (N.J.S.A. 46:8-43 et seq.) provide guidance on these matters, ensuring that late fees are reasonable and not punitive. Additionally, New Jersey contract law does imply a duty of good faith and fair dealing in contractual relationships. A landlord charging late fees for rent that is only an hour late could potentially be seen as acting in bad faith, especially if the lease does not explicitly state that rent is due by a specific hour and that time is of the essence. It is important for both landlords and tenants to be aware of these legal principles to ensure fair and lawful practices in the landlord-tenant relationship.