When producing an invoice in Workshop > Invoicing > Produce Invoice, it duplicates on another field e.g. when you add an Environmental charge £100 it will cause an additional charge to be added to the ‘collision waiver’ field £20 (see below image) causing the total non-labour charge to increase to £120.
In order to solve this you will need to remove the non-labour invoice calculation parameter within Workshop > Parameters > Non-Labour Charges > Invoice tab.
Click on the line which is causing the problem and delete – this will then remove the automatically calculated charge.
Return to Workshop > Invoicing > Produce Invoice – and search for the invoice.
Remove charges added previously and re-enter – additional charges will no longer be added to other fields (see image below)
Note that any other charges will need to be added manually as they will no longer be automatically calculated within the parameters.