Click the Enroll button next to Select Your Due Date. Submit the form at least two weeks prior to the payment due date.For returns filed and paid within 30 days of the due date, the penalty calculation is a graduated scale per NAC 360.395. Final payments to the prime contractor are due within 30 days of occupancy, use, or notice of completion of the project; whichever is earlier. Payments must be paid within 10 days of the due date to avoid penalty. Payments made or postmarked after this period must include the penalty. Select Your Due Date. Choose the payment date that works best for you. Tax rates are set in June of each year. Most transactions are available via the online portal, SilverFlume, and will be processed the same day for no additional charge.