Tex. R. Civ. P. 172
When an investigation of accounts or examination of vouchers appears necessary for the purpose of justice between the parties to any suit, the court shall appoint an auditor or auditors to state the accounts between the parties and to make report thereof to the court as soon as possible. The auditor shall verify his report by his affidavit stating that he has carefully examined the state of the account between the parties, and that his report contains a true statement thereof, so far as the same has come within his knowledge. Exceptions to such report or of any item thereof must be filed within 30 days of the filing of such report. The court shall award reasonable compensation to such auditor to be taxed as costs of suit.
Tex. R. Civ. P. 172