As I understand your question, it is now September, and you did not pay quarterly estimated tax at the April 15 and June 15 intervals. Is that the case? Even if you pay in a full “make-up” at this date, you are facing a penalty amounting to an interest charge on the missed payments.
Here is an end run around this situation. You mentioned you are retired. This says to me that you are over 59 1/2 years old. You have an option, available to you until Dec 31 of your tax year, to order your IRA custodian to send withheld tax payment direct to the IRS. The IRS considers payment made even in the 12th month to have been paid timely for the year.
