I'm new to QuickBooks Self-Employed and my 2018-2019 Tax Summary is showing GST on sales. I do not need to pay GST nor am I registered. I have now disabled it for future transactions but need to remove for last financial year. Thank you!
Unfortunately the only way to remove GST on sales in the past financial year would be to enter each invoice one-by-one and deselect GST, then save the invoice. I'm glad to hear that you have disabled GST for future transactions!