An HMRC investigation is not the end of the world. But for a UK founder or director who has never been through one, it can feel that way.
The truth is that most HMRC enquiries are routine. What makes the difference is whether your records are in order, your tax returns are accurate, and your adviser knows what to do.
This guide explains what triggers an HMRC investigation in 2026, how the different types of enquiry work, and what you can do now to protect your business before HMRC ever makes contact.
1. The Two Main Types of HMRC Enquiry
Aspect Enquiry
HMRC focuses on one specific area of your tax return. This could be a particular expense line, an R&D claim, or a VAT figure that does not match other data HMRC holds. Aspect enquiries are the most common type and, when handled correctly, tend to be resolved relatively quickly.
Full Enquiry
HMRC examines your entire tax return and financial records. These are more serious, take longer, and usually indicate that HMRC has identified a meaningful concern. A full enquiry is more likely to arise when HMRC sees multiple risk indicators at once.
2. What Triggers an HMRC Investigation
HMRC uses a combination of data matching, risk profiling, and random selection. Understanding what raises a red flag helps you manage risk before a return is ever filed.
Common triggers include:
- Significant changes in reported profit or turnover from one year to the next, with no obvious explanation
- Profit margins that are unusually low compared to businesses in the same sector
- Large or first-time R&D tax relief claims, particularly if documentation is weak
- High levels of director expenses or personal costs passed through the company
- Repeated VAT repayment claims, which signal to HMRC that input tax may be overstated
- Inconsistencies between the figures on your corporation tax return and your VAT returns
- Late or amended returns, which can indicate uncertainty or retrospective adjustments
- Tip-offs from third parties, including former employees or business partners
HMRC also uses Connect, an advanced data analysis system that cross-references information from banks, land registries, Companies House, and other sources. A lifestyle or asset that appears inconsistent with reported income can also prompt a closer look.
3. How HMRC Opens an Enquiry
HMRC must open a formal enquiry within 12 months of the date your return was filed. This is called the enquiry window.
You will receive a written notice under Section 9A of the Taxes Management Act 1970 for self-assessment returns, or Section 11A for corporation tax returns. The notice will state what HMRC wants to examine and ask you to provide information within a specified timeframe.
If HMRC suspects fraud or serious non-compliance, it may open an investigation under Code of Practice 9 (COP9). This is a more formal and potentially more serious process and requires specialist representation.
4. What HMRC Can Ask For
Once an enquiry is opened, HMRC can request a wide range of documents and information. This typically includes:
- Bank statements for both business and, in some cases, personal accounts
- Sales invoices, purchase invoices, and expense receipts
- Payroll records and employee contracts
- Details of any loans between directors and the company
- Contracts with customers and suppliers
- Board minutes and shareholder records
HMRC can request information going back up to six years for careless errors, and up to 20 years in cases involving deliberate non-compliance. This is why good record-keeping from day one is not optional.
5. The Five Areas Most Commonly Examined in Tech Businesses
R&D claims: HMRC has significantly increased scrutiny of R&D claims since 2022. Claims that lack detailed technical narratives or accurate cost apportionment are most at risk.
IR35 and contractor status: If your business engages contractors and falls outside the small company definition, HMRC will examine whether the off-payroll working rules have been applied correctly.
Director loan accounts: Loans from the company to directors must be properly documented and either repaid or treated as income. Unexplained overdrawn director loan accounts are a common trigger.
VAT on mixed supplies: Tech businesses that sell a combination of taxable and exempt services must apportion VAT correctly. Errors here are frequent and can result in meaningful adjustments.
Overseas payments: Payments to non-UK entities, including intercompany transactions with GIFT City or other overseas structures, are subject to withholding tax rules and must be evidenced at arm’s length.
6. How to Prepare Before an Enquiry Arrives
The best time to prepare for an HMRC investigation is before you receive one.
- Keep complete records for a minimum of six years. For R&D claims or complex tax positions, keep them longer.
- Reconcile your VAT returns against your corporation tax figures at least annually.
- Document director loans and ensure they are cleared or reported within the required timeframe.
- If you claim R&D relief, maintain a technical narrative for each project that clearly explains the advance sought and the uncertainty involved.
- For contractor engagements, keep the Status Determination Statement (SDS) on file for every contractor your business engages.
- Use qualified advisers to prepare complex claims. The standard of professional advice supporting a claim is one of the factors HMRC weighs in an enquiry.
7. What to Do If You Receive an Enquiry Notice
Do not respond directly to HMRC without taking professional advice first. The way you respond in the early stages of an enquiry can shape the entire process.
Key steps:
- Acknowledge receipt of the notice within the stated timeframe to avoid penalties for non-compliance.
- Engage a tax adviser or accountant with experience of HMRC enquiries immediately.
- Gather the documents HMRC has requested before the deadline, but do not provide more information than is asked for.
- Keep records of all correspondence with HMRC in writing.
If HMRC proposes an adjustment you disagree with, you have the right to request a statutory review and, if necessary, appeal to the First-tier Tax Tribunal.
Final Thoughts
Most HMRC enquiries do not result in significant additional tax. What they do result in is time, cost, and disruption. A business that is well-organised, files accurately, and keeps complete records is a much less attractive target than one that does not.
Preparation is the most effective protection available. If your records are in order and your claims are properly documented, an HMRC enquiry is a process to manage, not a crisis to survive.
Want to Make Sure Your Business Is Enquiry-Ready?
Book a free consultation with our UK tax specialists at SustainEdge Global.
We will review your current records, identify any areas of risk, and help you build the documentation needed to respond to HMRC with confidence.
