Option 1 :- Maintain balance bill by bill : Yes 

The error arises when the setting ‘Maintain bill by bill’ is ‘Yes’ in the ledger creation

Please fill data in column name Bill Name. It should not blank, If you don’t have data for this column then,

 please copy Invoice No and  paste inBill Name then generate xml file again. Try importing the newly

 created XML file, it should work.

Option 2 :- Maintain balance bill by bill : No

If, it is ‘No’ then you don’t need to enter the ‘Bill name’. You can keep it Blank.