HMRC Compliance Check 2026: What Triggers One and What to Expect

HMRC compliance in 2026: a data-rich landscape

When most people picture an HMRC investigation, they think of a physical audit with an inspector arriving at their office. The reality in 2026 is almost entirely different. The vast majority of compliance activity begins with a computer — specifically HMRC's Connect analytics platform — flagging an anomaly between a taxpayer's declared figures and data from dozens of third-party sources.

Understanding how this works, and what to do if it flags you, is essential knowledge for any self-employed person, landlord, company director, or investor.

HMRC's Connect: the digital compliance engine

Connect was introduced in 2010 and has been continuously upgraded since. As of 2026, it processes data from:

• UK banks and building societies: bank account balances, interest payments, transactions
• Land Registry: property ownership, purchase prices, remortgages
• Companies House: director appointments, company accounts
• Online marketplaces: eBay, Etsy, Airbnb, Vinted, Amazon seller data (mandatory reporting since January 2024)
• Social media and online presence: publicly visible lifestyle indicators
• Common Reporting Standard (CRS): overseas bank account information from 100+ countries
• DVLA: vehicle registration, changes in vehicle ownership
• Electoral roll and public records
• Pension providers and investment platforms

Connect builds a picture of each taxpayer's likely income, assets and lifestyle. Where the declared tax return does not align with this picture — a low-income declaration alongside property ownership, expensive cars and significant savings — a risk score is generated and a compliance check may follow.

What triggers a compliance check

Automated risk flags

• Income or profit significantly below the industry average for your sector
• Expenses that are unusually high as a percentage of turnover
• Large unexplained year-on-year changes in income or claimed expenses
• Property ownership not reflected in rental income declarations
• Earnings from online platforms (reported by the platform to HMRC) not included in your return
• Overseas income or accounts not declared
• VAT returns inconsistent with Corporation Tax or self-employment income declarations

Voluntary third-party reports

HMRC has an online mechanism for reporting suspected tax fraud. Reports from former business partners, employees, ex-spouses, and competitors do reach HMRC's compliance teams. HMRC does not confirm whether it acts on specific reports, but it does investigate credible information.

Random selection

HMRC uses a statistical random selection process to conduct enquiries on returns that are not risk-flagged. This is partly a deterrent — knowing that even correct returns may be examined incentivises accurate filing — and partly a quality assurance mechanism. Being randomly selected does not imply any wrongdoing.

Connected party investigations

If HMRC investigates your employer, business partner, director colleague, or accountant and finds issues, related parties may be reviewed. A PAYE compliance check on an employer sometimes leads to enquiries into individual employees' benefits declarations.

Types of compliance check

Aspect enquiry

An Aspect enquiry focuses on a single element of your tax return. You receive a letter identifying the specific area HMRC wants to examine — for example:

• "We wish to discuss the property income declared on your 2024/25 return."
• "Please provide supporting invoices for the £12,000 entertainment expense claimed."

Aspect enquiries can often be resolved quickly with documentary evidence. The key is to respond within the stated deadline with clear, organised records.

Full enquiry

A Full enquiry is an examination of your entire tax return. These are more serious, more time-consuming, and typically involve multiple rounds of correspondence. Full enquiries often involve requesting bank statements, invoices, payroll records, and business accounts spanning several years.

Discovery Assessment

Outside the normal 12-month enquiry window (HMRC usually has 12 months from the date you filed to open an enquiry), HMRC can issue a Discovery Assessment if it "discovers" income or gains that were not adequately disclosed. Time limits:

A Discovery Assessment can reach back 20 years for deliberate fraud — potentially covering your entire working life.

What happens during a compliance check

Stage 1 — Opening letter: HMRC writes to you (or your agent) formally notifying you of the enquiry. The letter identifies the tax year(s) and issues under review and requests information.

Stage 2 — Information gathering: HMRC may request bank statements, receipts, contracts, invoices, correspondence, travel logs, and accounting records. You must comply with valid information requests; unreasonable refusal can lead to penalties.

Stage 3 — HMRC's analysis: inspectors review submitted documents and may ask follow-up questions. They may invite you to attend a meeting or conduct a telephone interview.

Stage 4 — Findings and amendments: HMRC writes with its conclusions. If it believes additional tax is owed, it will propose an amendment to your return.

Stage 5 — Resolution or appeal: you can agree with HMRC's findings, negotiate, or appeal via Statutory Review and/or the Tax Tribunal.

HMRC's investigative powers

HMRC has broad statutory powers including:

• Request any information reasonably required (s.9A TMA 1970 for individuals)
• Third-party notices: require your bank, accountant or other parties to provide information about you
• Visit your business premises (with appropriate notice or, in urgent cases, court-ordered)
• Interview under caution: if HMRC suspects serious fraud, it can conduct a formal interview under the Police and Criminal Evidence Act (PACE), meaning anything you say can be used in evidence

For most taxpayers, compliance checks never reach the criminal investigation stage. The vast majority are resolved with payment of additional tax, interest, and civil penalties.

Penalty structure: the decisive role of behaviour

HMRC's penalty system is calibrated to incentivise disclosure and honest behaviour.

"Unprompted" means you disclose before HMRC has reason to suspect you. "Prompted" means you disclose only after HMRC contacts you. The difference can be tens of thousands of pounds on a large underpayment.

Suspended penalties: in cases of careless behaviour, HMRC can agree to suspend a penalty for up to two years if the taxpayer agrees to take specific corrective actions (better record-keeping, proper use of an accountant). If the conditions are met, the penalty is cancelled at the end of the suspension period.

Voluntary disclosure: the better path

If you suspect your tax affairs may have errors — undisclosed rental income, offshore accounts not reported, incorrectly claimed expenses — the best course of action is almost always to come forward before HMRC contacts you.

HMRC operates specific voluntary disclosure programmes:

• Let Property Campaign: undisclosed UK rental income. Minimum penalty on disclosure.
• Worldwide Disclosure Facility: offshore income and assets. Can be done online.
• Business Tax Disclosure: for business income not previously declared.

Voluntary unprompted disclosure triggers the lowest possible penalties (potentially 0% for genuinely innocent errors). Being discovered and investigated triggers much higher penalties plus significant professional and personal stress.

Practical guidance for receiving an HMRC enquiry letter

1. Do not ignore it. There is no benefit to delay and significant risk.
2. Read it carefully. Understand exactly what HMRC is asking and by when.
3. Gather records. Pull together the relevant bank statements, invoices, receipts and accounts before you respond.
4. Consider professional advice. For any enquiry involving more than a few thousand pounds of potential liability, a specialist tax adviser (preferably a Chartered Tax Adviser, CTA) will typically save their fees many times over.
5. Communicate in writing. Keep records of all correspondence. Do not make concessions verbally that you would not commit to in writing.
6. Respond fully. Partial responses or evasion within a response can be treated as obstruction.

Sources

• HMRC: Compliance checks — your rights and obligations (gov.uk)
• HMRC: Let Property Campaign — voluntary disclosure facility
• HMRC: Worldwide Disclosure Facility
• Taxation Management Act 1970, s.9A — enquiry powers
• HMRC: Compliance check penalties — factsheet CC/FS7a