Texas Tax Code - TAX § 151.012. Effective Date of Tax Rate Changes

(a) A change in the rate of the tax imposed under Sections 151.051 and 151.101 must take effect on the first day of a calendar quarter.

(b) If the performance of a taxable service begins before the effective date of a change in the tax rate and the performance will not be completed until after that effective date, the change in the tax rate applies to the first billing period for the service performed on or after that effective date.