Tex. Gov't Code § 823.303

A member who performs military service creditable in the retirement system but who does not establish credit for the service by making the deposits required by Section 823.302 is entitled to credit of a year for each year of military service performed, if the member requests the credit in writing before the later of the date of application for retirement or the effective date of retirement. The credit is usable only in determining eligibility for, but not the amount of, benefits under Section 824.406.