Written by the TaxTune Editorial Team · Reviewed by our qualified accountants · Updated for 2026
The quick answer The costliest VAT registration mistakes are registering late after crossing £90,000, missing the forward look test when a big contract lands, choosing the wrong scheme, not charging VAT from your effective date, and forgetting to reclaim pre registration VAT on stock and assets.

The mistakes that cost the most

  1. Registering late. Cross the £90,000 rolling threshold and fail to register, and you owe VAT you never charged, plus possible penalties.
  2. Missing the forward look test. If you expect to pass the threshold within 30 days, you must register immediately, not wait.
  3. Choosing the wrong scheme. The Flat Rate Scheme helps some and costs others. Check the maths before joining.
  4. Not charging from your effective date. You must account for VAT from your registration date, even before the number arrives.
  5. Missing pre registration VAT. You can often reclaim VAT on stock bought in the 4 years before registration and services in the 6 months before, if still used in the business.

Approaching or just past the threshold?

Timing and scheme choice make a real difference. TaxTune watches your turnover, registers you at the right moment on the best scheme, and reclaims the pre registration VAT you are owed.

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Frequently asked questions

What happens if I register for VAT late?

You are liable for VAT from the date you should have registered, even if you did not charge it to customers, and HMRC can add penalties. Monitoring the rolling turnover avoids this.

What is the forward look test?

If at any point you expect your taxable turnover to exceed £90,000 in the next 30 days alone, you must register straight away, rather than waiting for the rolling 12 month figure.

Can I reclaim VAT from before I registered?

Often yes. You can usually reclaim VAT on goods bought in the 4 years before registration that you still have, and on services in the 6 months before, if used in the business.

Do I charge VAT before my number arrives?

You must account for VAT from your effective date of registration. A common approach is to raise prices to include VAT and reissue proper VAT invoices once the number arrives.

How do I choose the right VAT scheme?

It depends on your costs and customers. The standard scheme suits most, while the Flat Rate or cash accounting schemes suit particular situations. It is worth checking the maths first.