Tex. Transp. Code § 460.601

In this subchapter, "tax increment" means the amount of revenue generated from ad valorem taxes, sales and use taxes imposed by a municipality under Section 321.101(a), Tax Code, or both ad valorem and sales and use taxes that are attributable to a public transportation financing area designated under this subchapter that exceeds the amount attributable to the area for the year in which the area was designated.