TLDR: This app's made our (slightly complex) multilingual EU-wide mixed B2C & B2B Shopify Plus store a lot more functional for our customers, and reduced the amount of headache we get from the EU VIES / VAT validation system. Review: As someone who decided to bite the bullet and upgrade to Shopify Plus after struggling with other EU VAT validation apps that do the validation separately on the cart page (BSS B2B & Wholesale 'Solution' particularly), this app's made the whole tax exemption process a lot more robust for us and reduced the amount of corrections required and customer complaints about these drastically. We are still required to use other apps to show additional messaging & custom coding to guide our customers, and also to convert the customers to companies on Shopify Plus manually (to ensure the VAT exemption is applied to the account / company location for future orders). However, as far as getting the first order in from the B2B customers in the EU; this app's helping us to get these in with the proper VAT validation and exemption already applied. The validation itself also seems to work a lot better than the official one in Shopify's backend (e.g. the German VIES database seems to be down all the time / unable to connect on Shopify - but we still may get orders coming in with the exemption applied even if the Shopify backend is not able to connect). I've also checked from the validation log (which is a great feature), that +95% of our customers have managed to do the validation successfully. And on the occasion the customer didn't manage to do it the first time (due to wrong format or database error), most of them have managed to do it eventually by trying again (which the app prompts them to do with the error messaging accordingly). Finally, while there were a couple of features that were missing from the app originally, these got implemented swiftly after requesting these (at our cost). What I'd still like to see: In addition to any performance and reliability improvements (if they're even possible due to how the VIES system works), one thing that is still missing is some kind of a 'fuzzy' search or automatic correction for special characters and common formatting errors. As an example: Belgian VAT numbers are commonly entered with a space and full stops as "BE 0123.456.789" - and the app will only accept "BE0123456789" (or with "be" "Be" "bE").