ORS 314.515: Installment schedule for payment of estimated tax.

(1) A corporation required under ORS 314.505 to make payments of estimated tax shall make the payments to the Department of Revenue in installments as follows:

      (a) One-quarter or more of the estimated tax shall be paid on or before the 15th day of the fourth month of the taxable year.

      (b) One-quarter or more of the estimated tax shall be paid on or before the 15th day of the sixth month of the taxable year.

      (c) One-quarter or more of the estimated tax shall be paid on or before the 15th day of the ninth month of the taxable year.

      (d) The balance of the estimated tax shall be paid on or before the 15th day of the 12th month of the taxable year.

      (2) Any payment of estimated tax received by the department for which the corporation has made no designation of the quarterly installment to which the payment is to be applied, shall first be applied to underpayments of estimated tax due for any prior quarter of the taxable year. Any excess amount shall be applied to the installment that next becomes due after the payment was received.