Okla. Stat. tit. 61, § 61-113.3: Interest - Rate

When interest is due the contractor, all awarding public

agencies, other than school districts, shall pay to the contractor

interest at the rate of one and one-half percent (1 1/2%) per month

of the final payment due the contractor. When interest is due to

the contractor, school districts shall pay to the contractor

interest at the rate of three fourths percent (3/4%) per month of

the final payment due the contractor. For lump sum contracts the

interest shall commence thirty (30) days after the work under the

contract has been completed and accepted and all required material

certifications and other documentation required by the contract have

been furnished the awarding public agency by the contractor, and

shall run until the date when the final payment or estimate is

tendered to the contractor.

For contracts bid by unit prices the interest shall commence

sixty (60) days after the above conditions are satisfied. When

contract quantities or the final payment amount is in dispute, the

interest-bearing period shall be suspended until the conclusion of

arbitration and settlement of the dispute.