HMRC has more access to data than ever before. They use advanced analytics, data-matching tools, information shared by banks and other government departments, and yes, even your social media profiles, to spot signs that something doesn’t quite add up. When they see inconsistencies or unusual activity, an investigation can quickly follow.

Below are some of the most common HMRC red flags business owners should be aware of.

1. Using a Personal Bank Account for Business 

Mixing personal and business transactions is one of the easiest ways to attract HMRC’s attention.

When you run everything through the same account, your records become messy and confusing. It becomes hard to show what’s business-related and what’s personal spending. This can lead HMRC to suspect that income is being hidden or expenses are being inflated.

A clean business bank account makes bookkeeping easier, protects you during an inspection, and signals that you’re organised and transparent.

2. Large or Unusual Cash Transactions 

Cash isn’t as common as it used to be, and HMRC knows that. So when they see large or frequent cash transactions, it naturally raises questions.

They may wonder: 

• Why so much cash? 
• Is all the income being declared? 
• Do the records match the cash activity? 

While cash isn’t a problem by itself, it does require detailed, accurate documentation. If HMRC senses anything unusual or inconsistent, they may look deeper.

3. Excessive or Unclear Expense Claims 

Expenses must be wholly, exclusively for business. If your claims appear unusually high for your industry or your explanation for them is vague, HMRC may suspect you’re overclaiming.

Some common triggers include:

• Claiming high travel expenses despite working mostly from home 
• Vague receipts or missing documentation 
• Trying to claim personal purchases as business expenses 
• “Entertainment” claims that don’t really qualify

Good record-keeping and clear justification go a long way.

4. Late Submissions or Payments 

Submitting tax returns or payments late (especially repeatedly) suggests disorganisation or avoidance. HMRC pays close attention to businesses that: 

• Miss multiple filing deadlines 
• Frequently pay VAT, PAYE, or Corporation Tax late 
• Ignore reminders or fail to respond to enquiries

If you appear to be falling behind, HMRC may decide to check whether everything else is in order.

5. Your Social Media Doesn’t Match Your Tax Returns 

It might sound surprising, but it’s true: HMRC checks social media.

If your online presence suggests a lifestyle or level of success that doesn’t match the income you’ve reported, this can trigger a review. 

For example:

• Posting about luxury purchases while declaring low profits 
• Advertising fully booked services but submitting minimal turnover 
• Sharing details of new staff, vehicles, or premises that aren't reflected in filings

If HMRC sees a mismatch, they investigate. Consistency matters.

Final Thoughts 

HMRC isn’t out to get you. They’re simply looking for signs that something doesn’t add up. By keeping clean records, separating personal and business finances, and staying consistent across your accounts and online presence, you significantly reduce your risk of an investigation.

A little organisation now can save you a lot of stress later.

If you’d like help reviewing your records, improving your bookkeeping systems, or making sure your business is HMRC‑ready, feel free to get in touch.