A common misconception is that all contracts must be written in order to be enforced; they do not. One of the exceptions to this rule is real estate leases because a special statue requires them to be in writing. Without a written lease, the tenant occupying and paying rent is subject to removal on a month’s notice.

Once the lease is executed, however, there are often claims that it was modified, and sometimes these modifications can be supported by evidence of conduct or several informal writings that, when considered together, show what the parties intended. Writings before the lease is executed are apt not to be seriously considered as including lease terms (absent fraud) because the lease is presumed by the law to encompass the full scope of the parties’ agreement after negotiations. Where the court cannot tell from the lease as written what the parties intended, prior negotiation correspondence may shed some light on what they mean.

More challenging is when a lease has been in place over a long period of time but sloppy amendments, emails, letters, statements, or conduct show that the parties’ agreement was constantly or periodically evolving. This is understandable when the parties are friends, cooperative, and helpful, but can make it difficult for a court to determine the actual terms when the friendship and cooperation end.

In the commercial lease context, remember that the personnel of the entities involved are subject to change. A relationship that is free and easy when the landlord’s manager is friendly could change dramatically when he or she is replaced.  Always document the terms of the lease important to you in writing in the original lease and in any modifications of it.