How do I add Wine Equalisation Tax onto my sales invoices?
You need to let forum members know what country you are in. There are thousands of taxation schemes around the world.
I am in Australia
Currently, Manager doesn’t have in-built support for WET. I think adding in-built tax code which will combine GST+WET will be relatively easy.
Until that is done, what you can do in meantime is to create a liability account called WET liability or WET payable in your Chart of Accounts.
Then on sales invoices, you can add new line item which will use WET liability account. The only issue is that you will need to calculate WET amount manually on invoice.