Ninety Thousand and Counting: What Really Happens When VAT Comes Knocking

There's no letter. That's the part UK founders find strangest. HMRC doesn't send a congratulatory card when you approach the VAT threshold; you find out on a Sunday evening, adding up a quarter's invoices, that your rolling twelve-month total is £86,400 and the next two invoices will tip you over.

What happens next depends almost entirely on how early you started thinking about it. Here's what changes, what it genuinely costs, and how to plan without slamming the brakes on growth.

The rule, in plain English

The main test is a rolling one. At the end of any month, if your taxable turnover for the previous twelve months goes over £90,000, you have to register for VAT. Registration takes effect from the first day of the second month after the month you crossed. Cross in August and you're VAT-registered from 1 October — which means those months in between aren't a grace period, they're a deadline.

There's also a forward-look test: if you expect to go over £90,000 in the next 30 days alone, you register, and registration is backdated to the start of that 30-day window.

The threshold has been parked at £90,000 since April 2024 and has survived a few Budgets without moving, but it's a political number rather than a law of physics. Check gov.uk before making decisions on it. The deregistration threshold is £88,000, which gives you a small buffer — not a reason to hover suspiciously close to the line.

What actually changes on day one

Three things, roughly in order of how much they surprise people.

Your prices get a 20% haircut, or your customers get a 20% rise. If you sell at £100 and absorb the VAT, you keep £83.33 before costs. If you add VAT on top, a £100 invoice becomes £120. There is no third option, whatever your accountant's tone of voice suggests.

Your invoicing gets specific. VAT invoices need particular fields — your VAT number, your customer's details, and the VAT rate and amount shown separately. Most accounting software handles it. Word templates and cheerful spreadsheets do not, and mistakes get expensive.

Your filing becomes digital. Making Tax Digital for VAT applies to every VAT-registered business, so you'll file through compatible software, usually quarterly, with payment due one month and seven days after the period ends.

The cash gap nobody warns you about

This is where growing companies get hurt. You charge VAT when you invoice. HMRC wants it roughly a month after your quarter closes. But your customers might pay in 45 or 60 days — or, if you sell to larger organisations, whenever their finance team gets round to it.

"I did the maths on a Friday and spent the weekend not sleeping," says Nadia, who runs a small supplier business in Birmingham selling to nurseries and schools. "We were going to be collecting thousands of pounds that belonged to HMRC while using it to pay wages. That's a horrible feeling."

Her fix was the VAT Cash Accounting Scheme, which lets eligible businesses account for VAT when customers actually pay rather than when they're invoiced. It doesn't erase the liability, but it lines the payment up with the money coming in.

Know which customers can reclaim

Here's the part that shapes your pricing strategy more than anything else. VAT is close to invisible for most B2B customers, because they reclaim whatever you charge them. A 20% rise is a line of paperwork, not a cost.

It's a completely different conversation if you sell to organisations that can't reclaim — charities, schools, some public bodies, and consumers. For them, your VAT-inclusive price is your real price, and 20% is 20%.

Nadia's customers mostly can't reclaim. "We couldn't send a letter saying the price is going up by a fifth and expect everyone to shrug. So we did it in stages, gave 90 days' notice, and held prices for anyone signing a twelve-month agreement before the registration date."

That cost her margin in year one. It also kept every customer.

Three decisions to make before you cross

Whether to absorb or pass on. Absorb and your margin takes the hit. Pass on and you find out how much your customers actually value you. Most founders land somewhere in between — absorbing on existing contracts, passing on for new ones.

Whether to use a scheme. Flat Rate, Cash Accounting and Annual Accounting all have eligibility rules and trade-offs. The Flat Rate Scheme looks generous until you meet the limited cost trader rules, which catch most service businesses and push the rate to 16.5%. Ask specifically about your sector before assuming it's a win.

Whether to register voluntarily. If you're sitting at £70,000 with strong input costs and B2B customers, registering early can pay: you reclaim VAT on equipment, software and subcontractors, and you look bigger than you are. That's a genuine strategic question, not a technicality.

The pre-threshold checklist

1. Pull your rolling twelve-month turnover and project it forward month by month.
2. Check the current threshold on gov.uk — don't rely on last year's number.
3. Split your customers into those who can reclaim VAT and those who can't.
4. Model both scenarios: prices held, and prices raised.
5. Draft the customer letter before you actually need it.
6. Talk to your accountant about schemes, cash accounting in particular.
7. Set up VAT-compliant invoicing in your software and test it on a dummy invoice.
8. Agree a filing calendar and diarise the payment dates for the first year.
9. Review your terms and conditions, including any early payment discount.
10. Update quotes and proposals to state clearly whether VAT is included.
11. Reprice for the next twelve months, not just today's order book.
12. Leave a buffer in your cash flow forecast for the first full VAT quarter.

The unglamorous upside

Crossing £90,000 is a milestone most founders would rather not be reminded of, because it arrives as an obligation rather than a reward. But it means something: you're selling enough for HMRC to take an interest.

Plan properly and you keep more of what you earn, plus you get a working system for reclaiming VAT on everything from laptops to ad spend. Plan badly and you spend your first VAT quarter learning about penalties. The founders who came through it well all did the same thing — they started six months early, and they treated it as a pricing problem rather than a tax one.