Tex. Labor Code § 204.048

(a) Notwithstanding any other provision of this subtitle, an employer for whom the commission has computed an experience rate as of October 1 of a calendar year that is effective for the succeeding calendar year, as provided by Section 204.047(a), may elect to make a voluntary payment of contributions to the commission.

(b) The amount of a voluntary contribution may be equal to all or part of the employer's chargebacks during the period ending September 30 that are used in computing the employer's experience rate for the succeeding calendar year. The commission shall allocate a voluntary contribution of less than the full amount of the employer's chargebacks first to the employer's most recent chargebacks.

(c) On receipt of a voluntary contribution during the period prescribed by Subsection (d), the commission shall reduce the employer's chargebacks by an amount equal to the contribution and shall recompute the experience rate applicable to that employer for the succeeding calendar year.

(d) An employer who elects to make a voluntary contribution for the recomputation of the employer's experience rate must make the contribution as prescribed by rules adopted by the commission. The employer may not revoke the contribution after the date on which the commission uses the contribution to recompute the employer's experience rate.

(e) Notwithstanding Subsection (a), the commission may not compute a new experience rate for an employer or reduce an employer's experience rate based on a voluntary contribution made by the employer after the expiration of the 120th day of the calendar year for which the rate is effective.

(f) The commission shall deposit a voluntary contribution made under this section to the credit of the compensation fund.