30 CFR §1290.111

If you neither pay nor appeal an order under this part, that order is the final decision of the Department, you have failed to exhaust administrative remedies as required under § 1290.110(a), and you may not contest the validity or merits of that order in any subsequent proceeding to enforce that order under 30 U.S.C. 1719 and part 1241 of this chapter.