30 USC 28f - Fee

(a) Claim maintenance fee 
The holder of each unpatented mining claim, mill, or tunnel site, located pursuant to the mining laws of the United States, whether located before, on or after August 10, 1993, shall pay to the Secretary of the Interior, on or before September 1 of each year, a claim maintenance fee of $100 per claim or site[1] Such claim maintenance fee shall be in lieu of the assessment work requirement contained in the Mining Law of 1872 (30 U.S.C. 28–28e)[2] and the related filing requirements contained in section 1744 (a) and (c) of title 43.
(b) Time of payment 
The claim maintenance fee payable pursuant to subsection (a) of this section for any assessment year shall be paid before the commencement of the assessment year, except that for the initial assessment year in which the location is made, the locator shall pay the claim maintenance fee at the time the location notice is recorded with the Bureau of Land Management. The location fee imposed under section 28g of this title shall be payable not later than 90 days after the date of location.
(c) Oil shale claims subject to claim maintenance fees under Energy Policy Act of 1992 
This section shall not apply to any oil shale claims for which a fee is required to be paid under section 2511(e)(2) of the Energy Policy Act of 1992 (Public Law 102486; 106 Stat. 3111; 30 U.S.C. 242).
(d) Waiver 

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(1) The claim maintenance fee required under this section may be waived for a claimant who certifies in writing to the Secretary that on the date the payment was due, the claimant and all related parties
(A) held not more than 10 mining claims, mill sites, or tunnel sites, or any combination thereof, on public lands; and
(B) have performed assessment work required under the Mining Law of 1872 (30 U.S.C. 28–28e)[2] to maintain the mining claims held by the claimant and such related parties for the assessment year ending on noon of September 1 of the calendar year in which payment of the claim maintenance fee was due.
(2) For purposes of paragraph (1), with respect to any claimant, the term related party means
(A) the spouse and dependent children (as defined in section 152 of title 26), of the claimant; and
(B) a person who controls, is controlled by, or is under common control with the claimant.

For purposes of this section, the term control includes actual control, legal control, and the power to exercise control, through or by common directors, officers, stockholders, a voting trust, or a holding company or investment company, or any other means.

(3) If a small miner waiver application is determined to be defective for any reason, the claimant shall have a period of 60 days after receipt of written notification of the defect or defects by the Bureau of Land Management to:
(A)  cure such defect or defects, or
(B)  pay the $100 claim maintenance fee due for such period.
[1] So in original. Probably should be followed by a period.
[2] See References in Text note below.