Hi Ben,
It could be the values you may have in the "Ref No" field -see the quote from suite answer below:
Ref No.
Ref No. is one of the key fields for the Expenses sublist. You can create a value for Ref No. when you create the expense report record. If you do not create a value, the system creates one.
If you create a value, note that it must be unique, and it must be an integer. If you attempt to populate the Ref No. field with an illegal value (such as an alphabetic value), the Import Assistant does not allow you to proceed past the mapping page.
Answer ID – 31844 also
https://netsuite.custhelp.com/app/an…ail/a_id/31839