N.D. Cent. Code § 43-07-23
Contracts entered between persons for the performance of work to be done by a contractor, except those contracts subject to section 40-22-37 or 48-01.2-13, or contracts governed by federal statutes or regulations which require other provisions with respect to retention, are subject to a maximum retention on amounts due under the contract as follows: retention of ten percent of each estimate presented is allowable until such time as the project is fifty percent complete, with no further retainage on estimates during the continuance of the contract. If the owner, governing board, or authorized committee invests the retained estimate funds, the interest earned on those retained funds is payable at the time of final payment on the contract to the contractor on whose account the moneys were held.
N.D.C.C. § 43-07-23