Standard intrastat declaration export file for Belgium should have only 10 columns
Now, standard file has 12 columns because row 9 (transport) and row 10 (incoterm) could be filled in case of extended declaration. But in case of standard declaration those columns should not be created otherwise the csv file imported to NBB is invalid.
Also, rows indexes for extended fields should be +1 (row[7] -> row[8] and row[8] -> row[9]) otherwise value row is replaced by transport.