How can I correct past GST errors on Xero from my online sales?

Dear All,

I have been selling via Shopify since last October and have now linked to my Xero accounting but I didn’t have all the settings correct in Shopify. When transactions come through to Xero they have not been showing the 10%GST that I need to collect. Is there a way to change the sales previously made to date to show the GST when uploaded to Xero.

I think I have set it up correctly for sales from today but it’s all the previous ones that are wrong.

Any help would be greatly appreciated please!

Many thanks

Rocket