Tex. Labor Code § 413.019: INTEREST EARNED FOR DELAYED PAYMENT, REFUND, OR OVERPAYMENT.

(a) Interest on an unpaid fee or charge that is consistent with the fee guidelines accrues at the rate provided by Section 401.023 beginning on the 60th day after the date the health care provider submits the bill to an insurance carrier until the date the bill is paid.

(b) Interest on a refund from a health care provider accrues at the rate provided by Section 401.023 beginning on the 60th day after the date the provider receives notice of alleged overpayment from the insurance carrier until the date the refund is paid.

Acts 1993, 73rd Leg., ch. 269, Sec. 1, eff. Sept. 1, 1993.