What Triggers an HMRC Investigation?

Receiving a letter from HMRC can be worrying, especially if it tells you that your tax affairs are being reviewed. While many people refer to this as an "HMRC investigation", HMRC officially calls these compliance checks. These checks are a normal part of the UK's tax system and do not automatically mean you've done anything wrong.

Understanding why HMRC may open a compliance check can help you reduce your risk, maintain accurate records, and deal with any enquiries confidently.

What is an HMRC compliance check?

A compliance check is HMRC's way of making sure that individuals and businesses are paying the correct amount of tax and claiming only the reliefs and expenses they are entitled to.

HMRC can carry out checks into almost any tax, including:

• Self Assessment
• Corporation Tax
• VAT
• PAYE
• Capital Gains Tax
• Construction Industry Scheme (CIS)

Importantly, a compliance check can end with:

• no changes at all;
• a tax refund if you've overpaid; or
• additional tax, interest and, in some cases, penalties if an error is found.

In other words, receiving a compliance check is not evidence of wrongdoing.

What commonly triggers an HMRC investigation?

Although HMRC does not publish a definitive list of triggers, its guidance and compliance activity show that investigations commonly begin for one or more of the following reasons.

1. Errors or inconsistencies in tax returns

One of the biggest reasons HMRC opens a compliance check is where figures appear unusual or inconsistent.

Examples include:

• income that differs significantly from previous years without explanation;
• unusually high business expenses;
• profit margins that fall well outside industry averages;
• mathematical errors or missing information; and
• discrepancies between different tax returns.

HMRC increasingly uses sophisticated data analytics to identify anomalies, so even genuine mistakes may prompt further questions.

2. Information that doesn't match HMRC's records

HMRC receives information from numerous sources, including:

• employers
• banks and financial institutions
• Companies House
• pension providers
• investment platforms
• overseas tax authorities through international information-sharing agreements

If the information you submit doesn't match data already held by HMRC, it may trigger further enquiries.

For example, failing to declare employment income, rental income, dividends or investment gains that HMRC already knows about is likely to attract attention.

3. Late tax returns or repeated late payments

Occasional late filing will not automatically lead to an investigation, but consistently filing returns late or repeatedly paying tax after the deadline may increase the likelihood of HMRC reviewing your affairs.

Regular compliance demonstrates good tax governance, whereas repeated failures can raise questions about record keeping.

4. Unusually high expense claims

HMRC expects businesses to claim legitimate business expenses.

However, exceptionally large claims compared with turnover or industry norms may prompt questions.

Examples include:

• excessive travel expenses
• unusually high motor costs
• significant home office claims
• entertainment incorrectly claimed as allowable
• personal expenditure included within business costs

Keeping clear evidence for every claim makes responding to any enquiry much easier.

5. VAT irregularities

VAT returns are routinely analysed for unusual patterns.

HMRC may review businesses where it identifies:

• frequent repayment claims;
• significant fluctuations in VAT;
• inconsistencies between VAT returns and other tax returns;
• missing VAT registrations; or
• unusually low VAT liabilities compared with turnover.

Businesses operating in sectors historically associated with VAT fraud may also experience increased scrutiny.

6. Industry-specific risk

Some sectors receive greater attention because they have historically shown higher levels of tax non-compliance.

These may include:

• construction
• hospitality
• retail
• taxi and private hire businesses
• beauty and personal care
• cash-intensive businesses

Being in one of these industries does not mean you will be investigated, but accurate bookkeeping is particularly important.

7. Third-party information

HMRC may receive information from:

• customers
• suppliers
• former employees
• whistleblowers
• other government departments

Where credible information suggests tax may have been underpaid, HMRC may decide to open a compliance check.

8. Random compliance checks

Not every investigation is triggered by a problem.

HMRC carries out a proportion of compliance checks completely at random to help measure levels of tax compliance across the UK.

This means even businesses with excellent records can occasionally be selected.

Does using an accountant reduce the chances of an investigation?

Having an accountant does not prevent HMRC from carrying out a compliance check.

However, working with a qualified accountant can significantly reduce the likelihood of errors that commonly trigger enquiries.

Professional accountants help ensure that:

• returns are submitted accurately;
• allowable expenses are correctly claimed;
• deadlines are met;
• supporting records are maintained; and
• any HMRC correspondence is handled promptly.

If HMRC does open a compliance check, having professional representation often makes the process far less stressful.

What happens if HMRC contacts you?

HMRC will normally write to explain:

• what tax is being checked;
• which tax years are involved;
• what information is required; and
• the deadlines for responding.

Depending on the circumstances, HMRC may ask to see accounting records, invoices, bank statements or other supporting documents.

Responding promptly and providing accurate information usually helps the process move more smoothly.

Can HMRC charge penalties?

Not every compliance check results in penalties.

Where mistakes are found, HMRC considers whether they arose because of:

• a genuine error despite taking reasonable care;
• careless behaviour;
• deliberate behaviour; or
• deliberate concealment.

The level of any penalty depends on the circumstances and is often reduced where taxpayers cooperate fully and make prompt disclosures.

How to reduce your risk

While no one can guarantee they will never receive an HMRC compliance check, you can greatly reduce your risk by following good accounting practices.

We recommend:

• keeping complete and accurate records;
• submitting tax returns on time;
• declaring all sources of income;
• retaining receipts and supporting evidence;
• claiming only genuine allowable expenses;
• seeking professional advice when unsure; and
• responding promptly to any HMRC correspondence.

Protect Yourself Against the Cost of an HMRC Investigation

An HMRC enquiry can be time-consuming and, in some cases, professional fees can reach up to £10,000. With Blue Rocket Accounting's HMRC Investigation Protection, the cost of our professional time is covered, giving you peace of mind if HMRC opens an enquiry into your Corporation Tax, VAT, PAYE, CIS or Self Assessment.

From handling every letter, phone call and meeting with HMRC to providing unlimited professional support with no hourly caps, we'll manage the process on your behalf so you don't have to worry about unexpected accountancy fees.

Cover starts from just £12 + VAT per month for businesses and £60 per year for individuals. To find out more or arrange your cover, get in touch with the Blue Rocket Accounting team today.

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