Tex. Code of Criminal Procedure § 5

The Comptroller of Public Accounts, upon receipt of a claim approved by the judge, shall examine it and, if he deems the claim in compliance with and authorized by this Article, draw his warrant on the State Treasury for the amount due the witness, or to any person to which the certificate has been assigned by the witness, but no warrant may issue to any assignee of a witness claim unless the assignment is made under oath and acknowledged before some person authorized to administer oaths, certified to by the officer, and under seal. If the appropriation for paying the account is exhausted, the Comptroller of Public Accounts shall file it away and issue a certificate in the name of the witness entitled to it, stating therein the amount of the claim. Each claim not filed in the office of the Comptroller of Public Accounts within twelve months from the date it became due and payable shall be forever barred.