Okla. Admin. Code § 260:10-3-3
The rate of interest for failure of an agency to make payment as specified in 260:10-3-1 shall be based on the per annum, computed on a 360-day calendar, per $100 per day. The rate of interest normally changes on July 1st of each year depending on the average interest rate for thirty day time deposits of State funds during the last calendar quarter of the last preceding fiscal year. The rate of interest shall be computed on a 360-day calendar. The State Treasurer shall report to the Director on July 1st of each year what the average interest rate was for the previous calendar quarter. The Director shall notify all agencies and publish on the OMES website what the interest rate shall be for the next fiscal year beginning July 1st.
Okla. Admin. Code § 260:10-3-3
Amended at 30 Ok Reg 1112, eff 7-1-13