Error - Book Keeper Windows | System.Argument Exception | DataGridComboBox 

If you are receive above message, follow below steps:

1. Edit your item against which this error is coming up

2. Check Default Tax Account,
    a. if it is GST@40%, make sure you have also made IGST@40%
    b. if it is IGST@28%, make sure you have also made GST@28%

Both GST and IGST tax account should be made for any new tax groups. https://bookkeeperapp.freshdesk.com/a/solutions/articles/1060000150007