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B2B handling: collect VAT ID and send it to FastBill

Use Shopify’s built-in VAT ID field to collect VAT ID (USt-IdNr.) during checkout and send them to FastBill automatically

The app sends the customer’s VAT ID (USt-IdNr.) and the company name from the billing address to FastBill. Company registration number and local tax ID aren't supported yet.

Setup (1 min)

In Shopify Admin

  1. Settings → Checkout

  2. Under Customer information, set Company VAT number to Optional

  3. Save

Note: Shopify applies reverse charge to valid VAT numbers on eligible EU cross-border orders. Checking the VAT number at checkout needs Shopify Tax (free up to Shopify’s yearly sales limit, then Shopify may charge a fee). This is up to Shopify: our app reads the VAT number once Shopify saves it on the order or the customer.

How it works after setup:

Step 1 – Customer enters VAT ID

The customer enters their VAT ID at checkout, and Shopify checks it in VIES right away.

Always with the country code: Shopify saves the VAT number only in the EU format, with the country code first (for example DE123456789). If the customer types it without the country code (123456789), they can enter it, but Shopify doesn't save it on the order, so it never reaches FastBill or the document. For a VAT ID without the country code, use Address line 2 (Option 2 below).

The VAT number field appears only after the Postal code (ZIP) and Country/region are filled in:

Step 2 – VAT ID is saved to the customer

Shopify saves it under Customer → VAT number.

This works for checkout orders and for orders you create in the admin.

Step 3 – We send the VAT ID to FastBill ✅

We send the VAT number to your invoicing system with the customer details, so it appears in the right place on the document.

Option 2: Address line 2

Instead of the checkout VAT number field, the customer can type the VAT ID in Address line 2 of the billing address.

Why Address line 2? It's more flexible than the checkout field: Shopify keeps a VAT number only with the country code, but what the customer types in Address line 2 goes to FastBill with or without the country code, exactly as typed.

Support can turn it on if you need it. The setting shows only in stores where it's already on.

With it on, the app sends what the customer typed in Address line 2 as the VAT ID, and leaves that line out of the address.

If both methods are on, the checkout VAT ID wins when there is one.

Important: the app doesn't check what's in Address line 2. Anything typed there goes to FastBill as the VAT ID, and the customer counts as a company (B2B). So rename the field in your Shopify checkout, for example to VAT ID, so customers don't type an apartment number there.

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