43 U.S. Code § 493 - Operation charges; date of payment; discount; advance payment
All operation and maintenance charges upon projects existing prior to December 5, 1924, shall become due and payable on the date fixed for each project by the Secretary of the Interior, and if such charge is paid on or before the date when due there shall be a discount of 5 per centum of such charge.
All contracts providing for new projects and new divisions of projects approved after December 5, 1924, shall require that all operation and maintenance charges shall be payable in advance. In each case where the care, operation, and maintenance of a project or division of a project are transferred to the water users the contract shall require the payment of operation and maintenance charges in advance. Whenever an adjustment of water charges is made under sections 371, 376, 377, 412, 417, 433, 438, 462, 463, 466, 467, 473, 474, 478, 493, 494, 500, 501 and 526 of this title the adjustment contract shall provide that thereafter all operation and maintenance charges shall be payable in advance.
 See References in Text note below.
First paragraph of this section is comprised of part of first sentence of section 6 of act Aug. 13, 1914. Remainder of first sentence of such section 6 is classified to sections 479, 494, and 495 of this title; second and third sentences of such section 6 are classified to sections 496 and 497 of this title, respectively.
Second paragraph of this section is from act Dec. 5, 1924.
Language was inserted in the first paragraph of this section limiting it to projects existing prior to Dec. 5, 1924, to avoid conflict with second paragraph applicable to projects after Dec. 5, 1924.
The definitions in section 371 of this title apply to this section.