A €40,000 invoice arrives from a German machinery supplier. At the bottom, one line: zzgl. 19 % USt. — plus 19% VAT. Your AP clerk's instinct is to pay it. Your controller's instinct is to ask whether a buyer sitting outside Germany should be paying German VAT at all. Both instincts are half right, and the space between them is where cross-border payment tax quietly gets expensive.
"Tax" is not one line on the remittance advice. It is three separate regimes that only look like one: transaction taxes on the supply (VAT and GST), withholding taxes on the payment itself, and customs duties on goods. Each one has a different trigger, a different party legally on the hook for it, and a different route to getting it back. Collapsing all three into a single mental bucket is the most common — and the most costly — mistake finance teams make when they first move payments across borders.
Three taxes, one invoice
Before doing anything else, decide which of the three regimes applies to each payment. They behave nothing alike.
| Tax | What it actually hits | Who charges or withholds it | Who can recover it |
|---|---|---|---|
| VAT / GST | The supply of goods or services (consumption tax) | The supplier — or the buyer, under reverse charge | The buyer, if registered and entitled to full input recovery |
| Withholding tax | The payment to a non-resident: interest, royalties, some fees, dividends | The buyer, who deducts and remits it to its own tax authority | The supplier, usually as a credit at home — not as cash back |
| Customs duty & import VAT | Goods physically crossing a border | The importing customs authority | Import VAT often recoverable; duty generally is not |
Figure: the three regimes behind a single "tax" line. Most cross-border invoices touch at least two of them at once.
VAT and GST: follow the customer, not the supplier
For business-to-business services, most modern VAT and GST systems put the place of supply where the customer is established, not where the supplier sits. That single principle explains why a French software vendor can invoice a Spanish business at zero VAT, with a note reading autoliquidation or "reverse charge". The tax has not vanished. It has moved to the buyer's own return.
The reverse charge only works because both sides are taxable businesses. Break that assumption and the logic flips: sell the same service to a consumer in that country and the supplier may be required to register and charge local VAT, which is what the EU's One Stop Shop and similar regimes exist to simplify. The business-to-business versus business-to-consumer boundary is the single biggest determinant of who has to register where — and it is decided by the nature of the customer, not the size of the invoice.
Here is why the reverse charge is not a rounding error. An Italian company buys €40,000 of consulting from a German supplier. The German supplier invoices €40,000 with no VAT and the reverse-charge note. The Italian buyer self-assesses Italian VAT on the purchase, and then claims the same amount back as input VAT. If the buyer recovers in full, the cash effect is zero. But if that buyer is partially exempt — a bank, an insurer, a healthcare provider with mixed activities — the input VAT it cannot reclaim becomes a real, permanent cost. The identical invoice is free for one buyer and a five-figure expense for another, purely because of the buyer's own VAT recovery position.
Withholding tax: the money taken at the source
Withholding tax is different in kind. It is deducted by the payer and handed to the payer's own tax authority on payments made to non-residents. It targets passive and certain service income — interest, royalties, sometimes technical or management fees, and dividends. Domestic default rates can be punishing (the United States statutory rate on many payments to non-residents is 30%), and it is almost always reduced by a double-tax treaty — but only if the payer can document the recipient's residence and status.
That documentation is where the friction lives:
- US payers collect a W-8BEN-E (entities) or W-8BEN (individuals) so they can apply treaty rates instead of the statutory default.
- Most jurisdictions accept a certificate of tax residence issued by the supplier's own revenue authority.
- Some countries run pre-clearance schemes — the UK's treaty passport, for instance, lets a non-resident lender register once and have UK payers apply the treaty rate automatically.
When the paperwork is missing, the payer has no choice but to withhold at the higher domestic rate. The supplier is then left to reclaim the excess, which is slow and in some countries practically impossible. The operational rule follows directly: collect and validate the tax forms before the first payment, not after the first dispute.
Gross-up clauses decide who really pays
Most cross-border contracts answer the withholding question in a single sentence, and that sentence is worth more than the rest of the payment terms. Under a gross-up, the buyer must pay whatever it takes for the supplier to receive the full contract amount after withholding — the buyer absorbs the tax. Without it, the supplier bears the cost. On a €100,000 services contract with a 10% withholding tax, that single clause is a €11,111 swing in cash (a 10% gross-up, not 10% of the total), and it is rarely modelled anywhere in procurement.
Why a treaty does not always close the gap
Treaty relief usually works as a credit, not an exemption. The supplier pays (or is subject to) tax at source at the treaty rate, then claims a foreign tax credit at home against tax on the same income. Two things follow. First, the cash leaves the group temporarily even when the final bill is nil. Second, the credit only has value if the supplier has enough taxable profit at home to absorb it. A loss-making or thin-margin supplier gets little back from a treaty rate cut, which is exactly why they negotiate hard for gross-ups — and why buyers should price that into the deal rather than discover it at settlement.
The tax position quietly changes where you pay
The same commercial transaction can produce a very different tax result depending on which legal entity pays and which receives. Paying a supplier's local subsidiary can avoid withholding tax but invites transfer-pricing scrutiny over the intercompany price. Paying the parent directly is commercially simpler but triggers withholding. And a supplier that needs to charge local VAT on its invoice often must transact through a local entity at all. This is why "just pay the address on the invoice" is not a tax strategy — the legal identity behind the invoice is doing more work than the number.
A practical checklist for finance teams
- Classify before you pay. Goods, services, royalties, interest? Each one lands in a different regime with a different form and rate.
- Establish residency on both sides and validate tax IDs — for the EU, check VAT numbers through VIES rather than trusting the invoice.
- Collect tax forms at onboarding, not at first payment: W-8BEN-E for US payers, certificates of residence elsewhere.
- Do not read "zero-rated" as "no tax". Under reverse charge the tax exists; it simply moves onto your return.
- Model withholding and gross-ups into landed cost. A 10–30% deduction dwarfs any FX spread you are optimising.
- Diary the expiries. Exemption certificates and residence letters age, and an expired form reverts you to the default rate.
- Claim what is recoverable. EU businesses can use the electronic refund procedure; non-EU businesses have narrower routes. Unclaimed input VAT is a silent write-off.
- Keep an audit trail of who paid, from which entity, to which jurisdiction, with which documentation attached.
Where the payment layer carries the tax data
None of the above is hard in isolation; it becomes hard at volume, when tax treatment, invoice references, and remittance data have to travel with hundreds of payments across dozens of jurisdictions. When each payment leg carries its own tax and reference data, finance teams stop rebuilding the picture by hand. The mechanics of settling in the supplier's currency are covered in our guide to multi-currency B2B payments, and the funding decisions behind it in our guide to paying international contractors and freelancers, where tax forms and residence documentation are already part of the flow.
Two adjacent risks are worth planning for at the same time. Tax documentation failures and compliance screening failures both tend to surface as a held payment rather than a clear error — we unpack why in the companion piece on KYC, KYB and sanctions checks. And when the invoice is recurring rather than one-off, the tax and mandate questions multiply; that is the subject of our guide to B2B subscription and recurring payments.