Definitions

Start Date: The date the penalty starts for a specific unpaid tax liability. This date indicates the beginning of the first monthly period.

Multiple Start Dates are possible when there are different tax liabilities assessed at different times on the same module

The most common Start Dates are the normal return due date (RDD), the extended payment due date, and the twenty-second day after an assessment date of demand (23C Date)

In the case of an installment agreement, the start date for the reduced penalty rate is the later of 1/1/2000 or the transaction date of the TC 971/ Action Code 063

Monthly Period: The period that begins on the Start Date and ends on the numerically corresponding day in the following calendar month. If the following month does not have a matching day, use the last day of that month.