A business that leases real estate and improvements (buildings, etc.) in the form of space for offices, a warehouse, a restaurant, a nail or hair salon, a clothing store, a coffee shop, or other commercial (nonresidential) space will usually be required to sign a written contract known as a commercial lease agreement.

If the tenant (the business occupying the space) who signs a commercial lease agreement fails to pay the rent or continues to use the leased premises for a purpose other than as permitted by the lease agreement (after receiving notice of the improper use), the landlord may have the right to terminate the lease and lock the commercial tenant out of the space by changing the locks.

A commercial landlord’s ability to lock a commercial tenant out of the leased premises—sometimes referred to as one of the landlord’s self-help options or remedies because the landlord may be able to exercise these rights without going to court—depends on the specific language in the written lease agreement and the state's contract law.

For example, a state's contract law may determine if any breach of the lease agreement by the tenant was a material breach that might justify an extreme measure such as changing the locks.

Contract law in most states recognizes an implied duty of good faith and fair dealing between parties to a contract, and a commercial landlord who changes the locks on the leased premises because the tenant is a few days late paying the rent may be in breach of the landlord’s implied duty of good faith and fair dealing.

In Missouri, a commercial lease agreement is a binding contract between a landlord and a tenant, where the tenant leases property for nonresidential purposes such as offices, warehouses, or retail spaces. Should a tenant fail to pay rent or use the property in a manner not permitted by the lease, the landlord may have the right to terminate the lease. Missouri law allows landlords to use self-help remedies, such as changing the locks, but this is contingent on the provisions of the lease agreement and must be done in accordance with state contract law. Any action taken by the landlord must also respect the implied duty of good faith and fair dealing inherent in Missouri contract law. This means that a landlord must exercise self-help options, like lockouts, reasonably and not in a manner that is considered extreme or unjustified, such as in response to a minor or brief lapse in rent payment.