Accounts Receivable Penalties and Interest calculation on overdue items - FINT

Hello All,

I want to post penalty and interest on customer overdue items at an item level. I am able to post the interest using FINT; but i am unable to compute penalty; please find the detailed requirement below

As soon as an item is overdue;

Compute a penalty of $20 or 10% which ever is greater

Compute simple interest of 5% on Principal amount + Penalty.

As i mentioned; I am able to compute 5% interest on the principal amount, but i dont see any customizing to add the fixed penalty.

Can this be acheived by standard SAP or do i need to build some custom logic?

Regards,

Shilpa