How can I display my UK VAT number on FedEx commercial invoices for Shopify orders?

Your VAT number just needs to be saved once somewhere that consistently feeds into your commercial invoice, rather than re-entered per order. If you're already shipping FedEx orders through some solution on Shopify, it's possible there's a place to add this in your account or tax details, even if it isn't labeled exactly as "VAT number."

To add this reliably, you can use PH Ship, Rate & Track for FedEx, which lets you save your VAT number once in account settings so it's applied automatically to every FedEx commercial invoice going forward.