How Do I Calculate VAT Under the Flat Rate Scheme for Construction?

Summary

The VAT Flat Rate Scheme is a simplified way for small VAT-registered businesses to work out what they owe HMRC. Instead of tracking input VAT (on every purchase) against output VAT (on every sale) and paying the difference, you apply one fixed percentage to your total VAT-inclusive turnover and pay that. For a lot of tradespeople — especially those doing mostly labour, with relatively low material spend — the scheme can mean a genuinely simpler VAT return and, in some cases, a small cash benefit, because the flat rate percentages are set below the standard 20% rate to roughly account for the input VAT you give up the right to reclaim.

The scheme is not automatically the right choice. It suits businesses with low expenditure on VAT-able goods relative to turnover. It becomes a poor choice — sometimes actively expensive — for businesses that spend heavily on materials, plant, or fuel, because you lose the ability to reclaim input VAT on almost everything except a capital asset purchase over £2,000. There is also a specific trap for very low-spend businesses: the limited cost trader rule forces a flat rate of 16.5%, which wipes out most of the benefit regardless of your trade sector.

This calculator sets out the mechanics — which percentage applies to which type of construction work, how to work out whether you're a limited cost trader, and a full worked example comparing the flat rate result to what you'd have paid under standard VAT accounting for the same job. It also covers the one major restriction that catches construction businesses out: the flat rate scheme cannot be used for supplies that fall under the domestic reverse charge.

Key Facts

• What it replaces — instead of output VAT minus input VAT, you pay a single fixed percentage of gross (VAT-inclusive) turnover.
• General building or construction services (materials make up more than 10% of turnover) — flat rate 9.5%.
• Labour-only building or construction services (materials make up 10% or less of turnover) — flat rate 14.5%.
• Limited cost trader — if you spend less than 2% of your VAT-inclusive turnover on goods (or less than £1,000 a year even if that's more than 2%), you must use 16.5% regardless of sector. "Goods" excludes capital expenditure, food/drink, and vehicles/fuel in most cases — check HMRC's current definition before relying on a self-assessment.
• Rate applies to gross turnover — the percentage is applied to your total sales figure including the VAT you charged, not to the net (ex-VAT) amount.
• Input VAT is generally not reclaimable under the scheme, except on a single capital asset purchase of £2,000 or more (including VAT).
• Joining threshold — your VAT-taxable turnover must be £150,000 or less (excluding VAT) in the next 12 months to join.
• Leaving threshold — you must leave the scheme if your total business income (including VAT) exceeds £230,000 in the last 12 months, or you expect it to in the next 30 days.
• 1% first-year discount — new VAT registrants using the flat rate scheme get a 1 percentage point reduction off their applicable rate for the first year of VAT registration.
• Cannot be combined with the domestic reverse charge — if you supply construction services that fall under the CIS domestic reverse charge, those supplies must be accounted for outside the flat rate scheme, under normal VAT rules.
• VAT invoices still required — you must still issue VAT invoices showing VAT at the standard/reduced/zero rate that applies to the supply; the flat rate percentage is only used to calculate what you hand over to HMRC, not what you charge the customer.
• Standard VAT registration threshold — £90,000 taxable turnover (since April 2024) is the trigger for needing to register at all, separate from the flat rate scheme's own joining/leaving thresholds.
• Choosing the wrong sector category is a common error — you must pick the category that best describes your business's main activity; HMRC does not allow you to shop around categories for the lowest rate.

Quick Reference Table

Percentages shown are those currently published by HMRC for the construction-related categories in VAT Notice 733's flat rate table.

Detailed Guidance

What the Flat Rate Scheme actually does

Under standard VAT accounting, you charge your customer VAT at the appropriate rate (usually 20%), collect it, and separately reclaim the VAT your suppliers charged you on materials, plant hire, tools, fuel, and other business costs. You pay HMRC the difference. Under the Flat Rate Scheme, you skip that reconciliation entirely: you still charge your customer VAT normally on your invoices, but instead of working out input VAT versus output VAT, you calculate what you owe HMRC as a single percentage of your total gross turnover — the whole amount you actually received, VAT included.

This matters because the flat rate percentage is deliberately set lower than 20% to roughly compensate for losing the ability to reclaim input VAT. Whether that trade-off works in your favour depends almost entirely on how much VAT-bearing expenditure you have relative to your turnover.

Which category applies to you

HMRC's flat rate table splits construction-related work into two categories that trip up a lot of trades:

• General building or construction services — used where you supply and fit materials as part of the job (a builder buying and fixing kitchens, an electrician supplying and installing cable and fittings, a plumber supplying and fitting pipework and sanitaryware). The rate is 9.5%.
• Labour-only building or construction services — used where you provide only labour, with the customer or main contractor supplying all materials. The rate is 14.5%.

The distinction is based on the nature of your supplies, not a strict percentage test you calculate every quarter — but HMRC's own guidance uses the "10% of turnover" figure as the practical dividing line: if materials genuinely make up more than roughly 10% of what you turn over, you're general building; if it's less (because you're mostly hired for your labour, with materials supplied by someone else), you're labour-only. Get this wrong and you risk under-declaring VAT, which HMRC can challenge on a compliance check.

The limited cost trader trap

Regardless of which sector you'd otherwise fall into, if your spending on goods is very low — under 2% of your VAT-inclusive turnover, or under £1,000 a year even where that would be more than 2% — you are a limited cost trader and must apply 16.5% instead of your sector rate. "Goods" for this test means physical items used exclusively for the business — it specifically excludes capital expenditure, vehicles, fuel, and food/drink, which catches out van-based tradespeople who assume fuel counts.

This rule exists because HMRC identified that some services businesses were joining the flat rate scheme purely to profit from the gap between the standard rate and a low sector percentage, without genuinely low levels of expenditure. For a labour-only subcontractor with almost no material costs, 16.5% can end up higher than the 14.5% labour-only rate — meaning the limited cost trader rule can actively cost you money if you don't check it every VAT period.

Worked Example 1: General building services (9.5% rate)

A jobbing builder who supplies and fits materials invoices £20,000 net of VAT to customers in a VAT quarter, all standard-rated. VAT charged at 20% is £4,000, so gross turnover for the quarter is £24,000.

Flat rate VAT due = Gross turnover × Flat rate %
                  = £24,000 × 9.5%
                  = £2,280

Compare this to standard VAT accounting for the same quarter. Suppose the builder bought £6,000 of materials net of VAT (£1,200 VAT at 20%), plus other VAT-bearing expenses of £500 net (£100 VAT) — total input VAT of £1,300.

Standard VAT payable = Output VAT − Input VAT
                      = £4,000 − £1,300
                      = £2,700

In this example, the flat rate result (£2,280) is £420 lower than standard accounting (£2,700) for the same quarter — a real cash benefit, on top of the simpler paperwork. That benefit shrinks or disappears the more materials-heavy the job mix becomes, because every pound of input VAT you'd otherwise reclaim is a pound you're giving up under the flat rate scheme.

Worked Example 2: Labour-only services (14.5% rate)

A labour-only subcontractor, working for a main contractor who supplies all materials, invoices £20,000 net of VAT in the quarter (assume this falls outside the domestic reverse charge for this example — see below). VAT at 20% is £4,000, gross turnover £24,000.

Flat rate VAT due = £24,000 × 14.5% = £3,480

Under standard accounting, this subcontractor has very little to reclaim — say £400 net of VAT-bearing expenses (fuel excluded from the goods test, but a genuine VAT-bearing purchase like small tools), giving £80 of input VAT.

Standard VAT payable = £4,000 − £80 = £3,920

Here the flat rate result (£3,480) is £440 lower than standard accounting (£3,920). But check the limited cost trader test first: if this subcontractor's goods spend for the quarter is under 2% of £24,000 (i.e. under £480) or under £1,000/year, the 16.5% limited cost trader rate applies instead — 16.5% × £24,000 = £3,960, which would be more than the standard accounting result. This is exactly the scenario the limited cost trader rule is designed to catch, and it is worth checking every quarter, not just when you first register.

Interaction with CIS and the domestic reverse charge

The Flat Rate Scheme and the Construction Industry Scheme (CIS) are entirely separate systems that both apply independently — CIS deductions are calculated on the labour element of a subcontractor payment (see cis deduction calculator) and have no direct effect on your VAT return.

The domestic reverse charge for building and construction services is different: it directly restricts the flat rate scheme. Where you supply construction services to another VAT-registered, CIS-registered business (not an end user), the reverse charge applies and the customer — not you — accounts for the VAT. Because you don't charge or collect VAT on those supplies, they cannot be included in a flat rate calculation. If any of your income falls under the reverse charge, you must account for that portion of your turnover under normal VAT accounting rules, alongside whatever flat rate turnover you have from customers the reverse charge doesn't apply to (mainly private homeowners). In practice, many subcontractors who work mostly for main contractors within CIS find the flat rate scheme delivers little or no benefit once most of their turnover sits inside the reverse charge.

Should you join?

The flat rate scheme tends to suit:

• Labour-heavy trades with genuinely low material and equipment spend.
• Businesses that want simpler bookkeeping and are willing to trade a small amount of precision for that.
• Businesses in their first year of VAT registration, who benefit from the 1 percentage point discount.

It tends to be a poor fit for:

• Materials-heavy trades (kitchen fitters, bathroom fitters, anyone regularly buying significant stock).
• Businesses working mostly within the domestic reverse charge, where flat rate turnover shrinks to a small residual.
• Very low-spend businesses at risk of the 16.5% limited cost trader rate.

Run both calculations — flat rate versus standard accounting — using your actual recent quarter's figures before committing, and re-check periodically, because your materials-to-turnover ratio can shift the calculation from one quarter to the next.

Frequently Asked Questions

Do I still charge my customers VAT at 20% under the Flat Rate Scheme?

Yes. The flat rate percentage only affects what you pay to HMRC — it has no effect on the VAT rate you charge on your invoices. You still issue normal VAT invoices at 20% (or the reduced/zero rate that applies to the specific job), collect that VAT from the customer as normal, and separately work out your HMRC payment using the flat rate percentage on your gross turnover.

Can I reclaim VAT on my van or tools under the Flat Rate Scheme?

Generally no, except for a single capital asset costing £2,000 or more including VAT (for example, a significant piece of plant or a vehicle purchase that qualifies as a capital asset for the business), for which you can make a one-off input VAT claim outside the flat rate calculation. Day-to-day purchases — materials, consumables, smaller tools, fuel — are not separately reclaimed; the lower flat rate percentage is intended to account for this.

Which category do I use if I do a mix of labour-only and supply-and-fit work?

You choose the single category that best describes the overall nature of your business, based on where the bulk of your turnover comes from, rather than switching category job by job. If your business genuinely straddles both models in roughly equal measure, look carefully at HMRC's guidance and the underlying 10%-of-turnover materials test, and keep records that support whichever category you settle on in case of a compliance check.

What happens if I go over the £230,000 leaving threshold?

You must leave the Flat Rate Scheme and revert to standard VAT accounting from the date you exceed the threshold (or from when you had reasonable grounds to expect you would in the next 30 days). You then need to reconcile normal input and output VAT going forward. This is separate from — and much higher than — the £90,000 threshold that triggers the requirement to register for VAT at all.

Is the Flat Rate Scheme worth it if I mostly work for VAT-registered main contractors under CIS?

Often not, because most of that income will fall under the domestic reverse charge and cannot be included in the flat rate calculation at all — you'd end up running two systems in parallel for a shrinking pool of flat-rate-eligible turnover. Model your actual customer mix (private homeowners versus VAT-registered contractors within CIS) before assuming the flat rate scheme will simplify your VAT.

Regulations & Standards

• Value Added Tax Act 1994 — the primary legislation governing VAT, including the flat rate scheme provisions.

• VAT Notice 733: Flat rate scheme for small businesses — HMRC's detailed guidance, including the full table of sector percentages, the limited cost trader test, and joining/leaving rules.

• VAT Notice 735: Domestic reverse charge procedure — governs which construction supplies must be excluded from flat rate calculations.

• VAT Notice 708: Buildings and construction — general VAT treatment of construction services, relevant to correctly categorising supplies.

• VAT flat rate scheme — GOV.UK

• Flat rate scheme for small businesses (VAT Notice 733) — GOV.UK

• VAT registration thresholds — GOV.UK

• Register for VAT — GOV.UK

• VAT domestic reverse charge for building and construction services — GOV.UK

• Buildings and construction (VAT Notice 708) — GOV.UK

• vat for trades — VAT registration, CIS, and the domestic reverse charge explained in full

• cis scheme — CIS deduction rates and gross payment status

• cis deduction calculator — how CIS deductions are calculated on subcontractor payments

• pricing guide — how to price a job, including materials markup and break-even rates