What HMRC May Ask in Tax Investigations

A letter from HMRC can make even a well-run small business feel unsettled. Tax investigations are not always a sign that HMRC believes you have done something wrong. Sometimes a return is selected at random, figures do not match information HMRC already holds, or a particular type of claim needs further evidence. The right response is calm, prompt and organised.

For sole traders, landlords, taxi and Uber drivers, CIS workers and limited company directors, the practical issue is usually the same: can you clearly show how the figures on your return were calculated? Good records turn a stressful enquiry into a manageable process.

What happens when HMRC opens an enquiry?

HMRC will normally write to explain which tax return, period or issue it wants to review. Read the letter carefully. It should tell you what information is needed, how to provide it and the date by which HMRC expects a response.

An enquiry may cover the whole return or just one area. For example, HMRC may ask a landlord to support rental income and repair costs, a taxi driver to explain business mileage and vehicle expenses, or a contractor to provide evidence of CIS deductions. A limited company director may be asked about dividends, directors’ loan account entries or expenses paid through the company.

The scope matters. Do not assume that a request for one item means every part of your finances is under question. Equally, do not send a box of unrelated paperwork in the hope that more information will make the matter disappear. Give HMRC the documents requested, along with a clear explanation where one is needed.

An enquiry is not the same as a penalty

There is a real difference between HMRC asking questions and HMRC deciding tax has been underpaid. The first is an opportunity to explain and evidence the return. If an error is identified, the outcome will depend on the facts, including whether the mistake was reasonable, how quickly it is corrected and whether you took appropriate care.

Ignoring letters, missing response dates or providing incomplete answers can make matters harder. Early, open communication is usually the more sensible route.

Why tax investigations are triggered

HMRC does not publish a simple checklist of triggers, and no one can guarantee that a return will never be checked. However, enquiries can arise where the figures reported appear inconsistent with other data or with previous returns.

For a sole trader, a sharp fall in income alongside unusually high expenses may lead to questions. For a landlord, rental income may not align with information received from other sources. Construction workers can face queries where CIS deductions shown on statements do not match the figures claimed. Company directors may need to explain substantial expenses, changes in turnover or transactions between personal and company accounts.

A change is not automatically suspicious. Businesses have quieter periods, landlords face repairs, and drivers replace vehicles. The key is being able to show the commercial reason behind the numbers. Keep notes when something unusual happens, such as a long period off work, a major repair, a change in how you work or a one-off business purchase. That small habit can save time months later.

Records HMRC may ask to see

The documents depend on the enquiry, but HMRC may ask for records that support both income and expenses. Digital copies are usually easier to find and share than a pile of faded receipts.

Useful records include:

• sales invoices, till records, booking-platform statements and bank payments received;
• business and personal bank statements where transactions need to be explained;
• receipts and invoices for expenses, including vehicle, travel, tools, mobile phone and repair costs;
• mileage logs where mileage costs have been claimed;
• tenancy agreements, rent schedules and correspondence about property repairs;
• CIS statements, payslips and evidence of deductions;
• company records for dividends, expenses, loans and payments to directors.

The detail matters. A bank statement may show that money was spent, but not always what it was for or whether it was wholly for business use. A properly labelled receipt, invoice or note helps bridge that gap.

If records are missing, do not create replacements or guess. Explain what is unavailable, why it is missing and what alternative evidence you can provide. This might include supplier statements, email confirmations, appointment records or bank transactions. HMRC may accept reasonable evidence, but the strength of that evidence will vary.

How to respond without making things worse

Start by creating a single folder for the enquiry. Save the HMRC letter, copies of every document supplied and a record of every call or message. Write down the date, the person you spoke to and what was agreed. It is simple administration, but it gives you a reliable audit trail.

Next, separate what HMRC has specifically asked for from what you think it might ask later. Check your records before replying. If an explanation needs context, keep it factual and concise. For instance, if a vehicle repair cost is higher than usual, state what the repair was, when it happened and why it related to business use. Avoid emotional language or speculation.

Never alter records after receiving an HMRC letter. If you discover an error, deal with it openly. A prompt correction is far safer than trying to force the paperwork to fit a return already submitted.

If you cannot meet the deadline, contact HMRC before it passes. Ask whether more time is possible and explain what you are doing to obtain the information. An extension is not guaranteed, but silence is rarely helpful.

Common pressure points for small businesses

Mixing personal and business money is one of the most common causes of confusion. It does not automatically mean that tax is wrong, particularly for sole traders, but it makes every transaction harder to explain. A separate account for business income and costs can make record-keeping much simpler.

Cash income also needs particular care. Taxi and delivery work, trades and small local services may receive payments in several ways: cash, bank transfer, apps and card terminals. Record every payment method consistently. The total income should reflect the business activity, not merely the money that reached one bank account.

Expenses require judgement too. The test is not whether an item was useful, but whether it was incurred wholly and exclusively for the business. Some costs have mixed personal and business use, such as mobile phones, home working and vehicles. In those cases, keeping a sensible basis for the business proportion is essential.

For landlords, repairs and improvements can be a difficult distinction. Fixing an existing item may be treated differently from improving or replacing it to a higher standard. Keep invoices with enough detail to show exactly what work was carried out rather than relying on a vague card payment description.

When to get support

You do not need to deal with every HMRC question alone. Getting an accountant involved early can help you understand the request, organise evidence and respond in a measured way. This is especially useful if the enquiry covers several years, questions records you no longer have, or raises issues around property income, CIS, VAT or a limited company.

At Accountancy n Tax, we help local clients turn complicated paperwork into clear records and manageable actions. If you have received an HMRC letter and are unsure where to begin, a free, no-obligation consultation can give you a clearer next step. We take care of the detail while you stay informed throughout.

The best protection against future questions is not perfection. It is a routine you can maintain: keep records as you go, separate finances where possible, review unusual transactions and ask for help before a deadline becomes urgent. That approach keeps compliance simple and leaves more time for the work that grows your business.