9 min read

What Happens If I Forgot to Register for VAT?

You crossed a registration threshold in another country six months ago. You only just realised. The first reaction is panic. The second is "maybe nobody will notice". Both are wrong. Here is what actually happens, what it costs, and how to fix it on the cleanest path possible.

The short version

Late registration is a known scenario. Tax authorities have a process for it, and it is not as catastrophic as it feels. The cost has three components: back-tax (the VAT you should have charged), interest, and penalties. The size of the penalty depends almost entirely on whether you raise it before they do. Voluntarily disclosed late registration is treated as a compliance event; one discovered during audit is treated as evasion.

The single most important thing: do not keep selling. Every additional day of unregistered taxable supplies adds to the back-tax balance and worsens the penalty story. Take stock first.

What you owe (back-tax)

The day you crossed the registration threshold is the day your obligation to charge VAT started. Every taxable supply since then carries a VAT liability you did not collect. The back-tax is calculated on the gross amount you received, treated as VAT-inclusive (because you cannot retroactively go back to customers and demand VAT they did not authorise to pay).

Worked example: you sold €500,000 of B2C SaaS subscriptions to German consumers in the 18 months after crossing the threshold. The tax authority treats those receipts as gross-of-VAT. Back-tax = 500,000 / 1.19 × 0.19 = €79,832 in German VAT owed.

That is the principal. Interest and penalties go on top.

Interest

Most jurisdictions charge interest on late VAT from the date each return would have been due. Typical rates as of 2026:

Interest compounds in some jurisdictions, simple in others. For an 18-month back-tax exposure at 8%, expect roughly 8 to 12% added on top of the principal.

Penalties

Penalties are where voluntary disclosure pays off. Almost every tax authority has a tiered system that depends on whether you came forward voluntarily and whether you cooperated.

EU Member States

Penalties vary widely. Italy: 90% to 180% of unpaid VAT for failure to register, reduced to one-fifth if voluntarily disclosed. Germany: 5% per month up to 25% of the underpayment, plus criminal exposure for tax evasion if not voluntarily disclosed. France: 40% to 80% surcharge plus 0.4% per month interest. Most Member States have a self-disclosure mechanism that reduces penalties to roughly the interest amount, sometimes plus a single-digit surcharge.

United Kingdom

HMRC's failure to notify penalty is a percentage of "potential lost revenue" with the rate set by:

Unprompted, non-deliberate disclosures carry penalties from 0% to 30%, with the rate at the lower end if you cooperate fully. Prompted disclosures of deliberate concealment can reach 100% of the lost revenue.

Australia

The ATO charges a failure to register penalty plus shortfall interest. Voluntary disclosure typically reduces the penalty by 80%. There is also a registration date adjustment: the ATO will usually backdate registration to the date you crossed the threshold rather than further back.

Canada

CRA's gross negligence penalty is 50% of the unpaid tax, but routine late registration usually triggers a 10% failure to file penalty plus interest. Voluntary disclosure programs (VDP) can eliminate penalties entirely if you qualify.

Other jurisdictions

Most countries with non-resident VAT regimes (UAE, Singapore, Japan, Saudi Arabia, India OIDAR, South Africa, Mexico) have explicit voluntary disclosure paths. Common pattern: register backdated, pay the back-tax plus interest, accept a small fixed penalty. Without disclosure: full penalty regimes apply, which range from 25% to 200% of unpaid tax.

Step-by-step fix

1. Quantify the exposure

You need to know exactly which countries you are exposed in and how much you owe in each. The fastest way: upload your transactions (or sync Stripe) to our free VAT Exposure Dashboard. It maps each transaction to the right country, classifies B2B versus B2C, and flags every jurisdiction where you have crossed the threshold and by how much. No account required.

You usually find that exposure is concentrated. Most companies hit two or three countries hard before they hit ten. Prioritise by exposure size.

2. Pause additional unregistered exposure

For B2C, you have two options:

For B2B, validate every customer's VAT number. Many of your "exposed" sales may turn out to be reverse-charge B2B that did not need registration in the first place. The exposure dashboard separates these out for you.

3. Register backdated

Most tax authorities will register you with an effective date of when you actually crossed the threshold, not the date you applied. This is a feature, not a bug: it lets you pay the back-tax through the normal return process rather than via a special disclosure mechanism.

Application process by country:

4. File the back returns

Once registered backdated, file the missed returns chronologically. The back-tax is paid with each return. Some jurisdictions allow consolidated late filings (one return for the whole missed period); others require separate returns per period. Most are tolerant if you file in good faith, all the same time, and offer a clear payment plan.

5. Consider voluntary disclosure if available

Some jurisdictions (UK, Canada, Australia, several EU Member States) have explicit voluntary disclosure programs that go beyond simply backdating registration. They can:

The trade-off: VDPs require formal disclosure, often with legal representation, and you commit to full disclosure of all relevant facts. They are worth pursuing for large exposure (typically over €100,000 of back-tax).

6. Document everything

Keep a paper trail showing when you discovered the issue, what you did, and when. Tax authorities respond very differently to documented self-correction versus discovered non-compliance. Documentation is also important for board reporting, auditors, and (if you raise capital) due diligence. See the VAT due diligence guide.

How long do they look back?

Statute of limitations on VAT assessment varies:

Voluntary disclosure usually limits how far back the authority will assess to the documented period of non-registration plus normal interest, rather than the full statute. Discovered non-compliance can extend assessment back to the longest applicable limit.

The math: when does it pay to disclose?

Almost always. The expected cost of waiting is the probability of audit times the difference between voluntary and audit-discovered penalties. Tax authorities are increasingly using data-matching with payment processors, marketplaces, and customs to identify non-resident sellers. The probability of discovery for SaaS companies above six figures of unregistered exposure is high and rising.

An illustrative calculation for a SaaS company with €200,000 of back-tax exposure across the EU:

The delta between voluntary and discovered alone justifies disclosure even at low audit probability.

Practical reality: tax authorities want compliance, not punishment. They have dedicated voluntary disclosure teams who handle this exact scenario every week. The first call is the hardest, but the conversation is usually procedural, not adversarial. The rare exception is wilful long-term concealment.

Preventing the next one

Once you have fixed the immediate issue, set up monitoring so the next country's threshold does not catch you. Useful patterns:

What about future B2C threshold changes?

The EU is moving to broader thresholds under ViDA, and several non-EU countries (notably Japan, Korea, and South Africa) have signalled threshold changes for 2026 and 2027. Track changes via the 2025-2026 changes guide and the thresholds table.

Recap

The VAT Exposure Dashboard maps your transactions to every country where you have crossed a registration threshold. Free, browser-based, no account required. The fastest way to see what you owe and where.

Exposure Dashboard · Filing deadlines · Filing calendar

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