Checks EU VAT numbers live in VIES and applies the 0% reverse charge to valid business buyers in other EU countries.
Available Updated Oct 20, 2026Version 1.0.0CS-Cart, Multi-Vendor 4.17.2 – 4.21.x No core file edits
Built for
EU VAT Number Validation & Reverse Charge: overview1 of 17
What it does
For EU stores that sell to businesses in other EU countries. Customers enter their VAT number in the profile or at checkout; the add-on checks the format for all 27 EU countries, Northern Ireland and the UK, asks VIES live and shows the registered company name. Valid buyers from another EU country get 0% VAT through CS-Cart's own tax calculation, also when your prices include VAT. Domestic sales keep VAT. UK numbers can be checked with HMRC.
How it works
Install, enter your license key and your own VAT number. The VAT number field appears on the profile page and at checkout. While the buyer types, the result shows under the field and the checkout summary switches to Reverse charge, VAT 0%. In the admin panel each order has an EU VAT panel with re-check and review, the orders list filters reverse charge orders, and the log lists every check. Multi-Vendor vendors' own VAT numbers are checked and printed too.
Features
VAT number field on the profile page and at checkout, or your own field
Format check for the 27 EU countries, Northern Ireland (XI) and the UK (GB)
Live VIES check with the registered company name while the customer types
Automatic reverse charge (0% VAT) for valid buyers in another EU country, through the CS-Cart tax engine
Net prices when your prices include VAT, for both tax calculation methods and shipping
VIES consultation number, date, name and address stored with every order
VAT number and reverse charge note on invoices, your VAT number under the store address
Fallback when VIES is down: accept and flag for review, or charge VAT
Optional UK number check with HMRC
Order panel with re-check, orders filter and validation log
Multi-Vendor: vendor VAT numbers checked and printed on vendor invoices
Full page cache ready (4.21), CS-Cart and Multi-Vendor 4.17.2 to 4.21
What you get
Package
kv_eu_vat_validation-1.0.0.zip, installed through Add-ons → Manage add-ons
Updates & support
12 months included. Download new versions from your account and install them in Add-ons → Manage add-ons or the Upgrade Center.
License
1 production installation. Staging, dev and localhost are free and unlimited. The add-on keeps working after the update period ends. How licensing works
Compatibility
We list only the builds we install and test on. “Tested” means the full test plan was run on that build; “Supported” means the build is inside the supported range and uses the same hooks.
CS-Cart version and edition compatibility
CS-Cart version
CS-Cart
CS-Cart Ultimate
Multi-Vendor
Multi-Vendor Ultimate
4.22 and later
Testing next
Testing next
Testing next
Testing next
4.21.2
Supported
Supported
Supported
Supported
4.20.x
Supported
Supported
Supported
Supported
4.19.x
Supported
Supported
Supported
Supported
4.18.x
Supported
Supported
Supported
Supported
4.17.2
Supported
Supported
Tested
Supported
Before 4.17.2
Not supported
Not supported
Not supported
Not supported
Last tested build: Multi-Vendor 4.17.2, Oct 20, 2026Tested on: Multi-Vendor 4.17.2
Requirements
Platform
CS-Cart or CS-Cart Multi-Vendor 4.17.2 – 4.21.x
PHP
PHP 7.2.5 – 8.3, as supported by your CS-Cart version
Requirement
The cURL extension and outgoing HTTPS from the server to ec.europa.eu (VIES) and, for UK numbers, api.service.hmrc.gov.uk
Platform
Taxes set up in CS-Cart (Settings → Taxes) with rates for the countries you sell to
Platform
A license key from cs-cart.kaviolabs.com or a CS-Cart Marketplace license number
Core changes
None. Hooks and template overrides only
1.0.0
Oct 20, 2026
Latest
Added 12
VAT number profile field (contact information, profile page and checkout), added to the checkout "Customer information" block; any existing text field can be used instead.
Format check for the 27 EU countries, Northern Ireland (XI) and the UK (GB), with check digits for 18 countries.
Live VIES check (REST API) with the store VAT number as requester: registered name, address and consultation number; results cached (valid 24 h by default, invalid 1 h, outages 10 min).
Live result under the field on the profile and checkout pages (30 checks per visitor and hour).
Automatic reverse charge (0% VAT) for valid buyers in another EU country through CS-Cart's tax exemption calculation, including taxes included in prices (unit price and subtotal methods, shipping, payment surcharges).
Fallback when VIES is down: accept and flag the order for review, or charge VAT.
Optional UK number check with the HMRC "Check a UK VAT number" API 2.0.
VAT snapshot per order and Multi-Vendor sub-order; EU VAT panel on the admin order page with re-check and review; orders list filter.
VAT number, reverse charge note and consultation number on invoices and order summaries (document templates and classic invoices); store or vendor VAT number under the store address; document variable kv_vat.
Orders > EU VAT numbers: counters, setup warnings, manual check and validation log.
Multi-Vendor: vendors' own VAT numbers (core Tax number field) checked on save and printed on vendor invoices.
Full page cache support (4.21), domain-bound license check, self-healing upgrades.
Tested on Multi-Vendor 4.17.2. First release.
Does CS-Cart not do this already?
CS-Cart has a "Tax exempt" switch per customer. It removes VAT from every order of that customer, also domestic ones, and it never checks a VAT number. This add-on checks the number in VIES and applies the exemption only to the orders that qualify, using the same tax calculation.
Do I need an account for VIES?
No. VIES is a free public service of the European Commission. Enter your own VAT number in the settings to receive consultation numbers.
What is a consultation number?
A reference VIES returns when you identify yourself with your own VAT number. It proves that you checked the buyer's number on that date. It is stored with the order and printed on the invoice.
What happens when VIES is down?
Depending on the setting, the number is accepted (format and check digit must be right) and the order is flagged for review, or VAT is charged. Re-check flagged orders later on the order page.
Will customers pay the net price when my prices include VAT?
Yes. For reverse charge orders the VAT is taken out of the price, for both tax calculation methods, including shipping.
Can I sell to consumers in other EU countries as usual?
Yes. Without a VAT number nothing changes: your CS-Cart taxes apply.
Are UK numbers supported?
GB numbers get a format check, and a live check with HMRC once you add your HMRC application credentials. Northern Ireland (XI) numbers are checked in VIES and can get the EU reverse charge.
Does it work with B2B Registration & Approval?
Yes. When a registered customer has an approved application with a VAT number and leaves the VAT field empty, that number is used. If that add-on marks approved customers as tax exempt, the core exemption applies to all their orders and beats the reverse charge rules; the EU VAT numbers page warns you about it.
I use my own checkout layout and do not see the field.
Add the VAT number field to the Customer information block in Design → Layouts → Checkout (block content).
What happens to old orders if I uninstall?
Their totals stay as they are. The VAT data of orders (VIES answers, consultation numbers) and the field the add-on created are removed. Disable the add-on instead if you want to keep them.
Is my customers' data sent anywhere?
Only the VAT number (and your own number as requester) goes to VIES or HMRC. No names, addresses or IP addresses are sent.
Is this tax advice?
No. The add-on checks numbers and applies the rule described in Usage. Ask your accountant which sales qualify in your situation.
Add a released add-on to this order and save 15% on it. It uses the same edition and store domain.
EU VAT Number Validation & Reverse ChargeThis add-on
+
B2B Registration & ApprovalTrade account applications with business details, documents and EU VAT check, reviewed and approved into your wholesale groups.
$79
+
B2B Request a Quote (RFQ)Let business buyers request a quote for several products, send them an offer with your prices and let them check out at the quoted prices.
$99
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