When you import a statement for the first time you are required to map the columns on the statement file to the appropriate data fields in Clear Books. This mapping is then saved for future imports.
If the layout of the columns change on a statement file then you will need to delete the mapping and re-map the columns to the appropriate data fields again.
Navigate Tools > Import > Import Mappings.
Click on the delete icon to the right of the appropriate bank account.
Once the bank account mapping has been deleted head back to the Money > Import Tool and re-import the bank statement using the bank import guide.