Question about late charge calculation

Summary:

Late charge calculation only for above 180 days

Content (required):

I have a requirement from one of my customers on late charges. They want to calculate late charge only after 180 days.

For example, if an invoice is overdue by 240 days, they want to calculate the late charge for 60 days (240-180)

I have setup an interest tier as 0-180 days 0% and above 180 days 9%. When I ran the late charge program, it calculates the interest for 240 days at 9%. It is not calculating the interest for 60 days.

Is there any setup I am missing or is it the standard functionality? Can anyone please guide me how to achieve this?