Why intra-EU invoicing keeps breaking for cross-border startups

Published 2026-10-16

Your client is in Germany, your company is in France, and the invoice software is asking you to pick a VAT rate. Pick wrong and you either undercharge VAT you actually owed or charge VAT you should have left off entirely, and either mistake surfaces months later when your accountant reconciles the Déclaration Européenne de Services. The fix depends on one fact you probably haven't verified: is your customer a taxable person established in the EU, or not.

The one question that decides everything

Everything about VAT on a cross-border invoice hinges on a single check: is the customer an assujetti, a taxable person, established in another EU member state. Get the answer and the rest of the invoice writes itself. Skip the check and you're guessing.

Founders skip it because "EU client" feels like enough information. It isn't. A German GmbH buying your SaaS subscription is a different tax case than a German consumer buying the same subscription, and a VAT-registered business in Germany is a different case again from an entity that has no VAT number at all, because it falls under a VAT exemption or special regime in its own country.

This one question produces exactly three outcomes, and no invoice should leave your system until you know which one applies:

• ✅ Reverse charge applies when the client is a VAT-registered taxable person established in another EU country, and the business is B2B.
• ✅ Outside French VAT scope applies when the client is established outside the EU entirely.
• ⚠️ French VAT is due when the client is a consumer (B2C) or a non-taxable entity even if it sits inside the EU.

Most invoicing errors on this blog's reader profile trace back to treating all three as one case: "EU, so reverse charge." That shortcut is wrong often enough to matter, because it ignores whether the transaction is B2B or B2C and whether the buyer is actually a taxable person.

How a French company gets into the VAT system

Every French company is issued a numéro de TVA intracommunautaire the moment it registers, built from the letters FR plus the company's SIREN, the 9-digit identifier assigned at incorporation. That number is what makes the reverse-charge mechanism possible at all, because it is what your client's accountant and the French tax administration check against each other.

Founders often conflate SIREN with the other identifiers a French company carries, so it's worth separating them cleanly here since the confusion shows up constantly in cross-border invoicing conversations:

The VAT number uses the SIREN specifically, not the SIRET and not a KBIS reference. A bookkeeper who mixes these up on an invoice template creates a document that looks professional and fails a VIES check the moment a German accountant verifies it against the EU VAT number validation system.

EU B2B services: the reverse charge in practice

For B2B services supplied to a VAT-registered client established in another EU member state, the French supplier invoices without French VAT, under autoliquidation. The client self-assesses the VAT in their own country at their own rate, which is the entire point of the mechanism: it moves the VAT liability to the place of consumption instead of the place of supply.

The invoice itself has to carry specific wording, not a blank VAT line. It must state "Autoliquidation / VAT reverse charge" and show both parties' VAT numbers, yours with the FR prefix and theirs with their own country prefix. An invoice missing this wording, even at a correct 0% rate, is a weak document if the client or an auditor ever questions it.

The administrative step founders forget sits outside the invoice entirely: filing a DES, the Déclaration Européenne de Services, which reports intra-EU B2B service sales separately from the regular VAT return. This is not optional paperwork attached to the invoice. It is a standalone monthly declaration, and in our experience the mistake we see again and again is founders treating the DES as a formality they'll get to eventually, then discovering during a reconciliation or an audit that the invoices issued and the DES filed for the same period don't match. That mismatch is exactly the kind of discrepancy that triggers a closer look from the tax administration, and it is entirely avoidable with a correct monthly process from the first invoice onward.

Some founders running SaaS and agency models across France and Tunisia or Morocco lean on dual-entity structures for delivery reasons. The reverse-charge mechanism still governs any B2B service invoice the French entity issues to an EU client regardless of where the underlying work gets done, so the DES obligation doesn't disappear because production sits elsewhere.

EU B2C and non-EU clients: different rules, no shortcuts

B2C sales inside the EU follow a different rule set than B2B, and that rule set must be checked on its own terms rather than assumed to mirror the reverse-charge logic above. A SaaS founder billing individual consumers across several EU countries is not running the same VAT treatment as the agency owner invoicing a VAT-registered client company, even if both invoices say "Germany" at the top.

Services to clients established outside the EU are generally outside the scope of French VAT entirely, which is a simpler outcome than reverse charge but still needs the establishment check to confirm the client genuinely sits outside the EU rather than inside it under a structure that looks foreign on the surface.

This article focuses on the B2B reverse-charge case because that's where the majority of invoicing errors in this reader segment originate. But a founder selling to consumers, or selling into both EU and non-EU markets at once, needs a separate, specific check for each client category, not one template copied across every invoice the company issues.

The franchise en base question for small and early-stage companies

Below certain turnover thresholds, a small business can operate under franchise en base, a VAT-exempt status that removes the company from VAT collection and reverse-charge mechanics altogether while it stays under the ceiling. As of 2025 the figures commonly cited are €37,500 for services and €85,000 for goods, though these thresholds have shifted before and a lower threshold near €25,000 was proposed and then suspended. Verify the current figure before applying it to any specific company, because this is a number that moves.

This matters directly for early-stage SaaS founders, because a company sitting under the franchise threshold in its first year may not need to think about reverse charge or VAT invoicing mechanics at all yet. The moment revenue crosses the threshold, the company enters the standard VAT regime and every invoice issued afterward, including the EU B2B ones, needs the full reverse-charge treatment described above.

The practical risk here runs in both directions. A founder who assumes they're still under the threshold when they've crossed it skips VAT registration they actually need. A founder who assumes VAT treatment applies before they've crossed the threshold builds unnecessary invoicing complexity into a business that doesn't need it yet. Either way, this is a number to check against actual revenue, not a figure to memorize once and forget.

Want the full picture of what gets set up when a French SAS is formed, including VAT registration timing? Nounda's pricing page lays out exactly what's bundled into formation and what's handled separately during the first 90 days.

The 2026 e-invoicing and e-reporting reform on the horizon

Mandatory electronic invoicing between French VAT-registered businesses is phasing in, with the ability to receive electronic invoices required first, followed by the obligation to issue them, rolling out across 2026 and 2027. This is directional, not fixed: the calendar has been postponed repeatedly already, so treat any specific date you read, including this one, as something to verify against the current official timeline rather than something to build a permanent process around today.

The reason to care now rather than when the deadline finally lands is practical. A founder setting up invoicing and accounting workflows for a new SAS this year should choose systems and processes that can accommodate structured e-invoicing formats once the requirement is live, rather than building a workflow around current practice and rebuilding it under deadline pressure in a year. A pattern we observe working with founders on cross-border invoicing is that the companies who treat this as "someone else's problem until the deadline" end up doing a rushed systems migration right when they should be focused on client delivery.

This reform sits alongside the reverse-charge and DES obligations rather than replacing them. An EU B2B invoice under autoliquidation will still need to say so and still need DES reporting once e-invoicing becomes mandatory; the format and transmission mechanism changes, not the underlying VAT logic.

What this looks like when it goes wrong, and how to get it right the first time

A pattern we see with founders on this route: reverse charge gets applied to what was actually a B2C sale, or a run of EU B2B invoices goes out correctly on the invoice itself but the DES never gets filed to match. Both errors tend to surface the same way, during a routine accounting reconciliation or an audit, and both require restating several quarters of filings once discovered. That's a far more expensive fix than getting the check right on invoice one.

The checklist that avoids this is short and should run before every new cross-border client relationship, not just the first one:

• ✅ Verify the client's VAT number against the EU VIES database.
• ✅ Confirm the client's taxable status, meaning they are genuinely a business, not a consumer or a non-taxable entity.
• ✅ Confirm the client is established in an EU member state, or outside the EU, as the case may be.
• ✅ Apply the matching treatment: reverse charge for qualifying B2B EU sales, out-of-scope for non-EU, French VAT for B2C or non-taxable EU entities.
• ✅ State the treatment correctly on the invoice, including the "Autoliquidation / VAT reverse charge" wording and both VAT numbers where it applies.
• ✅ File the DES for the period where reverse charge B2B sales occurred.

The legal rule itself is not the hard part once it's written down clearly. In our experience, the accounting setup matters just as much as the founder understanding the rule, because a bookkeeper unfamiliar with cross-border SAS invoicing is often where the actual error originates, not a gap in the founder's own knowledge. A founder who understands the reverse-charge logic perfectly can still get a wrong invoice out the door if the person handling the books defaults to a domestic template.

Nounda sets up the French SAS with the VAT registration and accounting workflow configured correctly from the first invoice, not retrofitted after a filing error surfaces. This sits inside the first-90-days support that follows company formation: getting the numéro de TVA intracommunautaire active, briefing the founder on reverse charge and DES obligations before the first EU client contract goes out, and connecting the founder with accounting support that understands cross-border SAS invoicing rather than treating it as a standard domestic file. For specifics on scope and pricing, check your eligibility and talk through your invoicing setup before the first contract is signed.