The error may be caused because of an additional separator (Comma in case of a CSV file, Tab in case of a TSV file) or an empty column present on a particular line. Remove the separator and empty columns and save the file. Finally, import the file into Zoho Books, match the corresponding fields and it should work perfectly fine.
P.S: Also, while importing files, please make sure the columns do not have unncecessary separators(Commas or Tabs) or characters as this might lead to causing the above error.
and GST filing.