Why HMRC investigates SME businesses: 5 key triggers

For most business owners, a tax investigation is high on the list of things they’d rather avoid – and for good reason. These enquiries can result in financial penalties, unexpected tax bills, and even reputational damage.

With HMRC increasing its focus on compliance, small business tax investigations and those into individuals have risen in recent years. It’s estimated that the number of investigations increased by 23% over the last year, with approximately 255,000 cases closed. This makes it more important than ever for business owners to understand what can trigger an enquiry and take practical steps to reduce the risk.

Many people assume an investigation only happens if they’ve done something wrong – but that’s not always the case. A simple error, unusual changes in profits, or a high volume of cash transactions can all attract HMRC’s attention.

While there’s no guaranteed way to avoid an investigation, understanding what can raise red flags puts you in a much stronger position. In this blog, we’ll explore five common triggers for small business tax investigations and what you can do to keep your business compliant.

5 things that can trigger small business tax investigations

1. Significant fluctuations in profit

A sudden spike or a sharp drop doesn’t automatically mean you’ve done anything wrong, but it could prompt questions from HMRC.

There are plenty of legitimate reasons for profit fluctuations. You may have landed a major contract, invested heavily in growth, faced rising costs, or experienced a quieter trading period. Seasonal businesses – for example – often see their profits vary from year to year.

The key is making sure your records tell the story behind the numbers. Accurate bookkeeping and up-to-date financial records can help explain any unusual changes if HMRC comes a-knocking. Keeping invoices, receipts, contracts and supporting documents organised will make it much easier to answer any queries quickly and confidently.

If your profits are likely to fluctuate significantly, working with an accountant can help you stay on top of your finances and ensure your tax returns accurately reflect your business activity.

2. Industry-specific benchmarks

HMRC doesn’t look at businesses in isolation. It compares your income, profits, and expenses with others in the same sector to spot anything out of the ordinary. If your figures are significantly higher or lower than the industry average – you could come under scrutiny.

For example, a restaurant reporting unusually low profits or a construction business claiming much higher expenses may prompt questions.

That doesn’t mean your tax return is incorrect. Every business is different, and factors such as location, business model, and market conditions can all affect your bottom line.

The important thing is to make sure your records back up your figures. Keeping accurate accounts and holding onto supporting documents can help explain why your business doesn’t follow the typical pattern for your industry.

3. Late submissions

Missing a tax deadline can do more than result in a penalty. Repeated late submissions may also increase the chances of HMRC taking a closer look at your business.

Whether it’s a Self-Assessment tax return, Corporation Tax return, VAT return or PAYE submission, filing late can suggest that your records aren’t being kept up to date. While the odd oversight can happen, a pattern of missed deadlines could raise concerns about the accuracy of your tax affairs.

The good news is that this is one of the easiest triggers to avoid. Keeping on top of key dates, maintaining accurate financial records, and preparing your returns well in advance can help you stay compliant and avoid unnecessary stress.

4. Cash payments

Businesses that handle a lot of cash often face greater scrutiny from HMRC. That’s because cash payments are harder to track than electronic transactions – increasing the risk of errors or undeclared income.

Certain industries – including hospitality and retail – naturally handle more cash than others. There’s nothing wrong with that, but it’s important to have robust systems in place to record every transaction accurately. If the figures reported on your tax return don’t add up or seem inconsistent with the type of business you run – HMRC may ask for more information.

Good record keeping is your best defence. Keeping detailed sales records, issuing receipts, and regularly reconciling cash takings can help demonstrate that your income has been reported correctly.

5. Unusual expense claims

Claiming legitimate business expenses can reduce your tax bill, but unusually high or inconsistent claims could attract attention. If your expenses seem out of proportion to your income or significantly different from what’s typical for your industry, HMRC may want to know why.

This doesn’t mean you should avoid claiming the expenses you’re entitled to. Large one-off purchases, business expansion, or unexpected costs can all lead to higher-than-normal claims. The key is making sure every expense is wholly and exclusively for business purposes and supported by the right documentation.

How AAB can help

Tax investigations can be a scary prospect. Whatever your needs, our experts are here to help at every stage. For advice or to enquire about our Tax Investigation services, please get in touch with Amber Clouston,  Stuart Petrie, or your usual AAB contact.