Tex. Water Code § 49.158

Within 30 days after a district becomes financially active, the board shall adopt a fiscal year by a formal board resolution. The district shall notify the executive director of the adopted fiscal year within 30 days after adoption. The district may change its fiscal year at any time; provided, however, it may not be changed more than once in any 24-month period. After any change in the district's fiscal year, the district shall notify the executive director of the changed fiscal year within 30 days after adoption.