From our friends at Passport: Merchants are now the responsible party for paying and collecting VAT for orders under £135. It is still possible to ship with a Postal carrier but it is no longer Delivered Duty Unpaid (DDU) service. VAT payments are now the responsibility and presumed paid by the seller of record.
The full background can be found in this Port Logistics Group blog post.
What needs to change in Whiplash?
As soon as possible, all Customers shipping to the UK from the United States or Canada should apply for a VAT number. VAT settings can be managed from General Preferences.
Collecting tax in the shopping cart
You can collect DDP tax for Orders directly in your ecommerce software.
You can follow these instructions from Shopify to add regional tax overrides.