Example:

If the Start Date is August 31, the Monthly Period ends on September 30.

Penalty Rate: The fixed amount or percentage charged with respect to a penalty. For example the penalty rate for a Failure to Pay (FTP) Tax Shown on the Return IRC 6651(a)(2) is 1/1% per month or fraction of a month. The penalty is figured on the first day of the monthly period. The rate changes to 1% per month on:

The beginning of the first month following the tenth day after the Status 58 date or TC 971 with Action Code 035, or 069, or