Line 15: Overpayment occurs when line 13 is greater than line 10. In such cases, record the difference on line 15. - If you mistakenly deposit more than the correct amount for the quarter, you have two options with the IRS. They can either apply it to your next return or refund the overpayment. Only select one option and record it on line 15. - Important note: Never make an entry on both lines 14 and line 15.