The program for dunning print is managed in BTE (Business Transaction Event, trx FIBF) event 00001720: here it's indicated which fm has to be run for print.
SAP std uses FI_PRINT_DUNNING_NOTICE (sapscript) or FI_PRINT_DUNNING_NOTICE_SMARTF (smartform) ( function group F150), so you should copy these function and assign it to event 1720.
To send payment reminders to those business partners that have overdue items, you can issue dunning notices.
You can enter the text for the notices and the form required using the SAPscript word-processing program or with SAP Smart Forms.
for more detail abt process hust go through this sap help doc...
<b>Dunning correspondence is an exception because it is handled using correspondence functions of the Financial Accounting component. The Smart Form variant of the dunning form is used in Flexible Real Estate Management but you have to make the Customizing settings and access the dunning correspondence in the Financial Accounting (FI) component. To do this, choose:
SAP Customizing Implementation Guide -> Financial Accounting -> Accounts Receivable and Accounts Payable -> Business Transactions -> Dunning -> Basic Settings for Dunning -> Printout</b>
It looks like you're new to SAP. I suggest you use SmartForms and not SAPSCRIPT, as it is much "friendlier". The sap help is not bad to learn it. See transaction SMARTFORMS.
To configure the dunning printout you need to follow the instructions (documentation) you find in SPRO:
Financial Accounting -> Accounts Recievalbe and Accounts Payable -> Business Transactions -> Dunning.
Kishan's instructions on the BTE are there as well. Your FI guy should help you with this, especially the 'Basic Settings' and 'Dunning Procedure'.
There is example SmartForm F150_DUNN_SF which SAP provides (just copy it to a Z and change it), this info is also in the SPRO documentation.
And just a note: if I remember correctly, when you "Assign Dunning Forms", if you assign a SmartForm and not a SapScript the system at least in our version 4.7 "yells" at you (that the form does not exist), but allows you to save. You need to ignore this, I assume there is a note that fixes this - it doesn't recognize the SmartForm name - but it works.
The following link contains step by step procedure for generating and printing dunning letters for sponsor research customers
For maitaining dunning letters.
Please refer to foll links too.
Please reward for the same.