Tex. Nat. Res. Code § 161.314

The forfeiture is effective at the time the board meets and adopts a resolution directing its chairman to endorse on the wrapper that contains the papers of the sale or on the purchase contract filed in the land office the word "forfeited" or words of similar import and the date of the action and to officially sign the document. At that time, the land and all payments previously made are forfeited.