The one-sentence answer

Crossing €10,000 locks you into destination-country VAT for the rest of that calendar year and the whole of the next one, regardless of what your sales do in between; only if that following year also finishes at or under €10,000 can you revert to home-country VAT — and consider actually leaving the OSS scheme — from 1 January of the year after that.

This is a self-check aid, not tax advice. See the disclaimer at the bottom before you act on any date here.

The lock-in rule: why "under €10,000 again" isn't instant

The €10,000 test that decides whether you can use home-country VAT is a two-year test, not a current-year one. Article 59c of the EU VAT Directive lets you charge home-country VAT only if your combined cross-border B2C sales stay at or under €10,000 in the current calendar year and in the preceding calendar year. The moment either year goes over, the exemption is gone — and it doesn't come back just because a later year happens to be quiet.

Work through what that means for a seller who crosses mid-year:

Year What actually happens Home-country VAT allowed?
Year 1 (crossing year) Cross-border sales pass €10,000 in, say, March. Destination-country VAT applies from that sale onward for the rest of the year. No, from the crossing sale onward
Year 2 Cross-border sales might be tiny — say €3,000 all year. Doesn't matter: the test needs Year 1 (the preceding year) to have been ≤€10,000 too, and it wasn't. No — locked into destination VAT for the whole year regardless
Year 3 Now the test looks at Year 3 and Year 2. If Year 2 stayed ≤€10,000 (it did, above) and Year 3 also starts under it, the exemption is back. Yes, from 1 January of Year 3

Notice what did not reset it: Year 2's low sales on their own. It's the calendar flip to Year 3 — with a full clean prior year behind you — that restores the option to use home-country VAT and, with it, the option to stop needing OSS for new sales.

The threshold calculator tracks the current-year running total that trips this rule in the first place — this page is about what happens the year, and the year after, once it has.

Leaving the OSS portal itself, once you're actually eligible

The lock-in rule above is about which VAT treatment applies to your sales — it's separate from whether you keep your OSS registration. In practice most sellers keep using OSS through the lock-in period anyway, because it's still the easiest way to pay destination VAT in several countries through one return. But once you've genuinely cleared the lock-in — or you've simply stopped making cross-border B2C sales at all — deregistering from the scheme itself is a short, low-friction step:

Not the same thing: exclusion for non-compliance

A third scenario gets talked about in the same breath as "leaving OSS", and it's worth keeping firmly separate from the two above: being excluded by the tax authorities. That's covered in full on what happens if you register for OSS late — the short version is that missing three consecutive, reminded quarterly returns or payments gets you barred from the Union scheme, the Non-Union scheme, and IOSS for a mandatory two years (eight quarters). That quarantine has nothing to do with the threshold lock-in above, and nothing to do with a clean voluntary deregistration — it's a penalty for non-compliance, not a consequence of your sales numbers or your own choice to stop.

Three "you can't just leave" rules, side by side

These three get conflated constantly — even some VAT-advisory write-ups blur them together — because they all involve a wait before things go back to "normal". They're triggered by completely different things:

Rule Threshold lock-in Voluntary deregistration Exclusion (non-compliance)
What triggers it Your sales crossed €10,000 You choose to stop using OSS Repeated missed, reminded returns/payments
What it locks Destination-country VAT treatment on your sales Nothing — it's the exit step itself All use of OSS Union, Non-Union & IOSS
How long Rest of crossing year + all of the next year None 2 years (8 quarters)
Is it a penalty? No — automatic tax-treatment rule No — an administrative choice Yes — non-compliance sanction

What to do right now

Sources

Disclaimer

This page and the calculator are a self-check aid, not tax advice. The lock-in mechanics above describe the general EU-wide rule under the VAT Directive; exact portal deadlines, notification screens, and any national specifics can differ by member state and change over time. Verify your own dates and obligations against the EU Commission's One Stop Shop portal or an accountant before you rely on any date or step described here.