How to Add Company Billing Fields (Tax ID, Trade Registry) to Shopify Checkout

If you sell to businesses, you need more than a name and address at checkout. You need the company name, tax ID (in Romania, the CUI), and trade registry number, otherwise you can't issue a correct invoice or let your B2B customer deduct VAT.

The catch is that Shopify, out of the box, is built for selling to consumers. There's no ready-made "tax ID" field and it won't validate the number automatically. The good news: there are several clean ways to add these fields, from the native checkout editor to apps that validate the tax ID against the tax authority. Below we go through each one, with its limitations and, most importantly, how the data actually reaches your invoice.

Decide which fields you actually need

Before adding anything, decide what you collect. For a correct B2B invoice you typically need:

• Company legal name
• Tax ID / VAT number (with or without country prefix)
• Trade registry number
• Registered office address

Optional but useful: IBAN and bank (for bank-transfer orders), plus a "Buying as a business" checkbox that reveals the fields only when needed.

Don't ask for data you won't use. The fewer required fields you have, the fewer customers abandon the cart. Ideally the company fields only appear for people who tick that they want a business invoice, while individuals go straight through the standard flow with no extra friction.

The native route: custom fields in the checkout editor

Shopify moved to Checkout Extensibility, and in the checkout editor (Settings - Checkout - Customize) you can add custom text fields, depending on your plan. In practice you add a "Tax ID" field and a "Trade registry" field with no code.

Be honest with yourself about the trade-offs:

• The data is saved as order attributes, visible on the order page in admin.
• There's no validation: the customer can type anything, including a wrong number.
• You can't easily show/hide fields (B2B vs individual) without an app.

For a small store with few business orders, this is enough. You check the tax ID manually when you issue the invoice. The old checkout.liquid method is no longer recommended, it has been replaced by this system.

With an app: validation, conditional logic and control

When you want something robust, a checkout app (a Checkout UI extension) gives you far more control:

• Validate the tax ID against the tax authority and VAT against VIES, to catch wrong numbers.
• Conditional display: company fields appear only when the customer ticks "business invoice".
• Fields required only for B2B, without bothering individuals.
• Auto-fill company name and address from the tax ID.

Some advanced features (custom blocks anywhere in checkout) require the Shopify Plus plan. On standard plans you still have useful extensions in the App Store.

Practical tip: don't install three apps that do the same thing. Pick one, test a real order end to end, and only then set it live.

The part that matters most: getting data into the invoice

This is where most people go wrong. You can collect the tax ID perfectly at checkout, but Shopify doesn't issue invoices compliant with local law and doesn't push to national e-invoicing systems. So those fields have to flow automatically into your invoicing tool.

The clean solution is an integration between Shopify and a local invoicing provider (in Romania: Oblio, SmartBill, FGO and others). Check specifically that:

• The tax ID and registry number from the order map into the business-customer fields on the invoice, not just a note.
• The invoice is sent automatically to the national e-invoicing system where that's mandatory for B2B.
• The VAT rate and customer type (individual vs company) are chosen correctly.

If that mapping isn't set up, you'll be copying the tax ID from each order into the invoice by hand. Fine for a month, but a source of errors at volume.

Common mistakes and an option for the Basic plan

A few traps we see often:

• A required tax ID field for everyone: individuals get stuck and abandon the cart.
• No validation and no check at issuing time: you end up with wrong tax IDs on invoices.
• Data stays only in the order note and nobody moves it into the invoice.

If you're on a plan where the checkout editor limits your fields, one alternative is to collect the company data before checkout: add fields on the cart page (cart attributes) that carry over with the order. Not as elegant as in-checkout, but it works even on entry-level plans.

If you want this done once and done right, with tax ID validation and a real link to e-invoicing, message us on WhatsApp at MPO Web Studio. We'll show you a demo of how it looks before you pay anything.