Texas Tax Code - TAX § 111.054. Timely Filing: Mail Delivery

(a) If a tax payment or a report is placed in a U.S. Post Office or in the hands of a common or contract carrier properly addressed to the comptroller on or before the date the payment or report is required to be made or filed, the payment or report is made or filed on time.

(b) The receipt mark of a contract or common carrier or the postmark on a tax payment or report is prima facie evidence of the date on which the payment or report was delivered to a carrier or the post office. The comptroller or the person making the payment or filing the report may show by competent evidence that the actual date of delivery to the carrier or post office differs from the receipt mark or postmark.

(c) The comptroller may refund or issue credits for penalties and interest paid solely as a result of returns or tax payments timely mailed but postmarked after the required filing date.