It is possible to retrieve the UDF index number from Tally.ERP 9 Release 4.8 onwards. Export the master/voucher in XML format. An XML attribute Index, within the UDF List Tag, helps to retrieve the original UDF number corresponding to the data available within the objects associated with it. This UDF number will be available in the Index attribute in the UDF List Tag, even when the TDL is not attached or is unavailable. The Index attribute will be available for Simple as well as Aggregate UDFs.
For example,
Raam
In the above tag, the UDF number, 1010, is displayed as the value of Index attribute in the UDF List Tag.