A £100 job is not always a £100 sale once VAT is involved. If you are VAT registered, you need to know whether the price you have agreed is before or after VAT, what rate applies, and how much of the money you receive belongs to HMRC. Knowing how to calculate VAT makes quoting, invoicing and cash flow far less stressful.
For many small businesses, VAT is not difficult because the maths is complicated. It becomes difficult when prices are unclear, receipts are missing, or VAT is treated as income that can be spent. A simple, consistent process will help you stay organised and submit more confident VAT returns.
What VAT means for your business
VAT, or Value Added Tax, is a tax charged on many goods and services in the UK. If your business is VAT registered, you normally add VAT to eligible sales and collect it from your customers. This is known as output VAT.
You may also be able to reclaim VAT paid on eligible business purchases, such as software, materials, equipment or professional services. This is called input VAT. Your VAT return shows the difference between output VAT and input VAT. If you have collected more than you can reclaim, you pay the difference to HMRC. If your eligible input VAT is higher, you may be due a repayment.
VAT is not your profit. It is money you collect and account for on HMRC’s behalf, which is why putting it aside as you receive payment can protect your cash flow.
The VAT rates you need to check
The standard VAT rate is currently 20%. This is the rate that applies to many everyday business sales and purchases.
Some goods and services may be subject to the reduced rate of 5%, while others are zero-rated. Exempt supplies are treated differently again, and there are items on which VAT cannot be reclaimed. The right rate depends on exactly what you sell or buy, not simply on the type of business you run.
Do not assume that every expense has VAT on it, or that every customer invoice should include 20%. If you are unsure, it is worth checking before you invoice or claim. Getting the VAT treatment right at the start is much easier than correcting returns later.
How to calculate VAT at 20%
The calculation depends on whether you are starting with a price excluding VAT or a price including VAT. This is where many otherwise careful business owners get caught out.
Adding VAT to a net price
A net price is the amount before VAT. To add standard-rate VAT, multiply the net price by 20%, then add that amount to the original price.
For example, if you charge £100 for a service excluding VAT:
£100 × 20% = £20 VAT
£100 + £20 = £120 total price including VAT
Your invoice should clearly show the net amount of £100, VAT of £20 and gross total of £120. If you are VAT registered, this helps your customer understand what they are paying and, where relevant, reclaim their own input VAT.
A quicker way to reach the VAT-inclusive total is to multiply the net price by 1.20. So, £100 × 1.20 = £120.
Removing VAT from a gross price
A gross price already includes VAT. You cannot simply take 20% off the total to find the VAT element. That would give the wrong answer because the 20% is calculated on the net price, not the final total.
To remove 20% VAT from a gross price, divide the total by 1.20 to find the net amount. Then subtract the net amount from the gross amount to find the VAT.
If a customer has paid £120 including VAT:
£120 ÷ 1.20 = £100 net
£120 – £100 = £20 VAT
At the standard rate, there is also a handy shortcut: the VAT element of a VAT-inclusive total is one-sixth of the gross amount. For a £120 payment, £120 ÷ 6 = £20 VAT.
This matters when you have quoted a customer a single total price. If you say a job costs £600 and do not make it clear that VAT is extra, a VAT-registered business may need to treat £600 as VAT-inclusive. That would leave £500 as sales income and £100 as VAT, rather than £600 income plus VAT.
Calculating VAT at other rates
For the reduced rate of 5%, multiply the net price by 0.05 to find the VAT, then add it to the net amount. A £200 net sale at 5% VAT would have £10 VAT added, making the gross total £210.
To remove 5% VAT from a gross total, divide by 1.05. For instance, £210 ÷ 1.05 = £200 net, leaving £10 VAT.
Zero-rated sales are still usually reported on your VAT return, but VAT charged is £0. Exempt sales and purchases can affect what VAT you may reclaim, so they should not be treated as simply the same thing as zero-rated items. This is one area where tailored advice can save time and prevent avoidable errors.
Work out what you owe on your VAT return
Your VAT return adds up the VAT you have charged on sales and deducts the VAT you can reclaim on eligible purchases. Here is a simple example for one VAT period:
You invoice customers £6,000 net and charge £1,200 VAT. Your total sales value including VAT is £7,200. During the same period, you buy supplies and services costing £1,500 net, with £300 VAT that you can reclaim.
Your output VAT is £1,200. Your reclaimable input VAT is £300. The amount due to HMRC is £900.
The figures in real life can be more involved. You may issue credit notes, pay deposits, have unpaid invoices, use the Cash Accounting Scheme or deal with purchases where VAT is not reclaimable. The basic principle remains the same: keep each transaction recorded accurately and let your bookkeeping system build the return from clear information.
Make pricing and invoices clear from the outset
A surprising number of VAT problems begin before the work has even started. Make it clear in quotations, proposals and conversations whether your prices are “plus VAT” or “including VAT”. If you work mainly with consumers or clients who cannot reclaim VAT, VAT-inclusive pricing is often easier for them to understand. If you work mainly with VAT-registered businesses, showing net prices plus VAT may be more natural.
Your invoices should include the required VAT details, including your VAT registration number, invoice date, a unique invoice number, the tax point where applicable, and a clear breakdown of the net amount, VAT rate, VAT amount and total due. Good invoicing is not just about compliance. It also reduces queries and helps you get paid promptly.
Keep VAT money separate from day-to-day spending
When a customer pays a £1,200 invoice, only £1,000 may be available to cover your work, costs and profit. The remaining £200 is VAT you will likely need to pay over later, subject to the VAT you can reclaim.
A practical habit is to move the VAT portion of payments into a separate savings account. You do not need to make the transfer exact to the penny after every invoice if that does not suit your process, but regularly setting money aside creates breathing room when your VAT payment date arrives.
Cloud bookkeeping software can also help by applying the right VAT rate to sales and purchases, storing receipt images and showing an estimated VAT position. It still needs accurate information going in. Review your bank transactions, raise invoices promptly and ask questions when a supplier bill does not look right.
Common VAT mistakes to avoid
The most common mistake is charging VAT before you are registered, unless you are dealing with the specific period and rules around registration. Equally, do not wait too long if your taxable turnover means you need to register. Registration thresholds and rules can change, so check the current HMRC guidance or seek advice based on your circumstances.
Other frequent issues include using 20% as a deduction from a VAT-inclusive amount, reclaiming VAT from a receipt that does not show VAT, mixing personal and business spending, and forgetting to adjust for credit notes or refunds. Small errors can build up across a quarter, particularly when records are left until the filing deadline.
If you use a VAT scheme such as the Flat Rate Scheme, Cash Accounting Scheme or Annual Accounting Scheme, the way your return is prepared may differ. The standard calculations in this guide are a useful starting point, but scheme rules can change the final amount due.
VAT should feel like a routine part of running your business, not a last-minute worry. With clear prices, tidy records and a regular check of your VAT position, you can make decisions with confidence and keep more time for the work that grows your business. If the numbers are becoming a distraction, a friendly bookkeeping professional can help you put a calm, reliable process in place.