Does a Texas rent increase notice need to be in writing?

Yes. Texas requires a written notice for any rent increase on a month-to-month tenancy or at the end of a fixed term. Texas has no statewide statutory advance notice for rent increases. Lease terms govern. Default practice is 30 days written notice on a month-to-month tenancy, matching the Tex. Prop. Code 91.001 termination rule. No state rent cap, and local rent control is preempted. An oral notice is generally not enforceable; the tenant can refuse to pay the increased amount and the landlord cannot evict for nonpayment of an unwritten increase. The written notice should state the current rent, the new rent, the effective date (which must be after the statutory notice period), and the landlord's signature. Delivery follows the same service rules as other landlord notices: personal delivery, substituted service, or posting plus mailing.

Source: Lease-based; Tex. Prop. Code 91.001 (30-day month-to-month termination default)