Shopify now lets you toggle the use of preferential treaties in Duties and Import Taxes calculations at checkout. Preferential treaties (FTAs) between countries can reduce or eliminate duties on certain products if specific requirements are met. If these requirements aren't fulfilled, you can disable the treaties in the settings, and the calculator will default to the most-favoured-nation (MFN) duty rate.
→ Read the full update on changelog.shopify.com