Over the last couple of years, we have seen roughly 10 times the volume of HMRC inquiry letters compared to previous years. That is not an exaggeration. We track the amount of work we take on related to HMRC inquiries and investigations, and the data is clear.
The people receiving these letters typically aren’t tax dodgers. They are small business owners, sole traders, small landlords, and people selling online as a side gig. They are ordinary people who may have made a mistake, didn’t realize they had to declare income, or simply had poor record-keeping.
Here is exactly how to handle an HMRC investigation, what not to do, and how to come out the other side paying only what you actually owe.
Why This Is Happening Now
We are in 2026, and HMRC has invested heavily in technology over the past five years. Their Connect system pulls data from banks, payment platforms, online marketplaces, the Land Registry, the DVLA, and even social media.
If you have a National Insurance number and you have made money through almost any platform, there is a good chance HMRC knows about it. Every major platform is now legally required to report your sales directly to HMRC if you have had more than 30 transactions or earned more than £1,700.
HMRC is incentivized to investigate because every inquiry has the potential to recover unpaid tax or issue penalties. Even if you don’t owe any tax, they can fine you for not declaring properly.
The Main Red Flags That Trigger Scrutiny
If you are running a side business, renting a property, or selling a collection on eBay, you need to understand what puts you on HMRC’s radar.
- Unexplained Bank Deposits: If money enters your account that doesn’t match what you have declared, their system can automatically flag it. Whether it is a gift, loan repayment, or a one-off sale, if it is significant, HMRC may assume it is undeclared income.
- Late or Inconsistent Returns: A single late return isn’t the end of the world, but patterns matter. If you consistently file late, submit amended returns, or show dramatic profit swings year-on-year, this generates a risk score.
- High Expense Claims: If your expenses are unusually high for your industry and income level, it gets flagged. HMRC will compare your figures against industry averages.
- Platform Benchmarking: Platforms are scrutinized more than ever. If your activity looks like trading, that data is pushed to HMRC along with your personal identifiers.
Key Takeaway
Key Takeaway: HMRC’s “Connect” system now cross-references data from banks, online platforms, and the DVLA to automatically flag discrepancies. Investigations are no longer random; they are data-driven. A single innocent slip-up during an initial phone call with HMRC can escalate a routine check into a full audit spanning years.
You Received a Brown Envelope: What Next?
If a letter lands on your doormat, follow this process immediately.
Step 1: Do Not Panic And Do Not Call Yet
This is where many people go wrong. They get scared, call HMRC, and start explaining themselves. Everything you say can be used against you. Innocent slip-ups or misremembered details can change the entire direction of an inquiry.
Step 2: Identify the Letter Type
Is it a nudge letter asking you to check your returns because they think something might be wrong? Or is it a formal inquiry stating they believe you owe tax? The approach is different for each, but ignoring either is dangerous. Interest and penalties stack up, and debts can be handed to collection agencies.
Step 3: Assess Your Position Honestly
Do you have solid records? Can you prove your side of the story?
- Handle It Yourself: If your records are immaculate—bank statements, transaction histories, clear documentation—and you are confident you understand the rules, you may be able to resolve this yourself.
- Get Professional Help: If you have gaps in your records, missing bank statements, or unclear transactions, you are at risk. HMRC will ask for evidence, and if you cannot provide it, they will use their own estimates, which are rarely in your favor.
Why Professional Help Matters
Accountancy firms exist because there is a process to this. We know how to structure a response, present evidence, and identify allowable expenses you may not have considered. Negotiating with HMRC requires speaking their language.
Once you engage, the process typically follows these steps:
- Disclosure: An acknowledgement that you will cooperate.
- Documentation: You provide bank statements and records relevant to the inquiry.
- Review: HMRC reviews your data and may ask follow-up questions.
- Negotiation: We establish the actual facts—what you earned versus legitimate expenses—and negotiate the final figure.
Crucially, penalties are not set in stone. If you have been cooperative and the issue was a genuine mistake rather than deliberate evasion, penalties can often be significantly reduced.
Received an HMRC letter or worried you might be next?
Don’t handle it alone. We can review your position, handle all communication with HMRC, and help you negotiate the best possible outcome.
Don’t Let Fear Stop You
The real shame is seeing people close their eBay shops or stop their side hustles out of fear. We need entrepreneurs in the UK. We need people taking risks and building things.
Don’t let the fear of paperwork stop you. The goal is never to avoid paying tax you legitimately owe; it is to ensure you don’t pay more than you owe because the investigation was handled badly.
Get compliant. Keep perfect records. And if a letter arrives, don’t face it alone.
