Texas Election Code - ELEC § 86.005. Marking and Sealing Ballot

(a) A voter must mark a ballot voted by mail in accordance with the instructions on the ballot envelope.

(b) A voter may mark the ballot at any time after receiving it.

(c) After marking the ballot, the voter must place it in the official ballot envelope and then seal the ballot envelope, place the ballot envelope in the official carrier envelope and then seal the carrier envelope, and sign the certificate on the carrier envelope using ink on paper.  An electronic signature or photocopied signature is not permitted.

(d) Failure to use the official ballot envelope does not affect the validity of the ballot.

(e) After the carrier envelope is sealed by the voter, it may not be opened except as provided by Chapter 87.

(f) Expired.