@AlexMTN , while it is true that you can export Sales Orders from Acumatica to Shopify, and most of the data can be updated, Shopify’s order > billing info is immutable. Which means that as soon as you create an order, you cannot change billing information: neither manually, nor through API, nor through any kind of integration. The reasoning behind it is that Shopify is primarily serving retail, where merchants charge customers at the time of checkout. Adding an option to change billing info adds a risk of tax amounts changes, and as such, will invalidate the originally estimated and charged amount from a client.

Hope this helps.