Missouri Revised Statutes Title XXIX. Ownership and Conveyance of Property § 441.234. Tenant may deduct cost of repair of rental premises from rent, when--limitations

1. The provisions of this section shall apply only to a tenant who has lawfully resided on the rental premises for six consecutive months, has paid all rent and charges due the landlord during that time, and did not during that time receive any written notice from the landlord of any violation of any lease provision or house rule, which violation was not subsequently cured.

2. If there exists a condition on residential premises which detrimentally affects the habitability, sanitation or security of the premises, and the condition constitutes a violation of a local municipal housing or building code, and the reasonable cost to correct the condition is less than three hundred dollars, or one-half of the periodic rent, whichever is greater, provided that the cost may not exceed one month's rent, the tenant may notify the landlord of the tenant's intention to correct the condition at the landlord's expense. If the landlord fails to correct the condition within fourteen days after being notified by the tenant in writing or as promptly as required in case of an emergency, the tenant may cause the work to be done in a workmanlike manner and, after submitting to the landlord an itemized statement, including receipts, deduct from the rent the actual and reasonable cost of the work, as documented by the receipts, not exceeding the amount specified in this subsection; provided, however, if the landlord provides to the tenant within said notice period a written statement disputing the necessity of the repair, then the tenant may not deduct the cost of the repair from the rent without securing, before the repair is performed, a written certification from the local municipality or government entity that the condition requiring repair constitutes a violation of local municipal housing or building code. In the event of such certification, the tenant may cause the work to be done as described herein if the landlord fails to correct the condition within fourteen days after the date of said certification or the date of the notice from the tenant, whichever is later, or as promptly as required in case of an emergency. The tenant's remedy provided herein is not exclusive of any other remedies which may be available to the tenant under the law. No lease agreement shall contain a waiver of the rights described in this section.

3. A tenant may not repair at the landlord's expense if the condition was caused by the deliberate or negligent act or omission of the tenant, a member of the tenant's family, or other person on the premises with tenant's consent. A tenant may not deduct in the aggregate more than the amount of one month's rent during any twelve-month period.