UDF is required in Promo Master to capture various information related to Promotion and generate MIS later on. These UDF fields needs to be captured in POS Bill details also as the information can be chaged periodically as per need.
For example:
Vendor has agreed to share 50% of Promo Discount which shall be debited to them at the time of payment reconciliation. This terms keeps changing during the promo period and will be updated in Promo Master. At end of the period a report will be generated for the total Promo Discount given in POS Bill and against that what is the UDF% value which shall be debited to vendor.
Similar to this there are other informative parameter which shall be capture in UDF.