Hi PEZ,
I too have difficulties with the IOSS and Shopify. Where in Shopify were you able to add your IOSS ID number? My company is located in EU but my warehouse is outside of EU, so it seems like Shopify doesn’t support IOSS for customers like me. So how did you manage to make it work? Also, I was told that there is no way to create a threshold to only charge VAT on orders less than 150€.