No one plans to get hit with an HMRC penalty.
It usually starts small. A missed deadline. A return filed a bit late. Something overlooked because life got busy. Then the letters arrive.
What catches people out isn’t just the penalties themselves — it’s how quickly they stack up, and how easy they are to trigger without realising.
With Making Tax Digital for Income Tax (MTD IT) landing in April 2026, the number of reporting deadlines is increasing. That means more opportunities to get things wrong.
So what actually triggers an HMRC penalty in 2026? And more importantly, how do you avoid them?
The Main Types of HMRC Penalties
HMRC penalties fall into a few key categories. Understanding these is the first step to staying clear of them.
1. Late filing penalties
If you miss a Self Assessment deadline, HMRC applies automatic penalties.
For individuals, the standard structure is:
- • £100 fixed penalty (even if no tax is owed)
- • Additional daily penalties after 3 months
- • Further penalties at 6 and 12 months
This applies whether you’re a sole trader, landlord, or have side income to declare.
2. Late payment penalties
Paying tax late triggers a separate set of charges.
These typically include:
- • 5% penalty after 30 days
- • Further 5% penalties at 6 and 12 months
- • Interest charged from the due date
Even small delays can result in noticeable extra costs.
3. Inaccurate return penalties
If your tax return contains errors, HMRC may apply penalties based on behaviour.
The level depends on whether the mistake is:
- • Careless
- • Deliberate
- • Deliberate and concealed
Penalties can range from 0% up to 100% of the tax owed.
4. Failure to notify HMRC
If you should be registered for Self Assessment but aren’t, HMRC can apply penalties.
This often happens when:
- • Side income exceeds £1,000
- • Someone becomes self-employed
- • Rental income isn’t declared
The longer it goes unreported, the higher the penalty risk.
What Changes in 2026?
The biggest shift is the rollout of Making Tax Digital for Income Tax.
From April 2026, many sole traders and landlords will need to:
- • Submit quarterly updates
- • Maintain digital records
- • Complete an end-of-year declaration
This introduces a new system called points-based penalties for late submissions.
The New Points-Based System (MTD)
Instead of immediate fines, late submissions earn penalty points.
Each missed deadline adds a point. Once you hit a threshold, a financial penalty is triggered.
Typical thresholds are expected to be:
- • 4 points for quarterly submissions
- • 2 points for annual submissions
Once the threshold is reached:
- • A £200 penalty is issued
- • Further missed deadlines trigger additional £200 penalties
Points don’t last forever, but they don’t disappear quickly either. You’ll need a period of full compliance to reset them.
Why People Get Caught Out
Most penalties don’t come from complex tax issues. They come from simple things slipping through the cracks.
1. Deadlines multiply under MTD
Moving from one annual deadline to multiple updates increases the chance of missing something.
2. Poor record-keeping
If income and expenses aren’t tracked during the year, it becomes harder to submit accurate and timely returns.
3. “I’ll sort it later” mindset
Leaving everything until January has always been common. Under MTD, that approach stops working.
4. Not knowing you’re in scope
Many people don’t realise:
- • They’ve crossed the £1,000 side income threshold
- • Their turnover exceeds £50,000
- • They need to register or report
Real-World Scenarios
Scenario 1: The missed deadline
You forget to submit a quarterly update under MTD. You receive a penalty point. Repeat it a few times and a £200 penalty is triggered.
Scenario 2: The forgotten side income
You earn £2,000 from freelance work but don’t declare it. HMRC may treat this as failure to notify — penalties plus tax and interest apply.
Scenario 3: The rushed tax return
You file quickly without checking expenses or deductions. Inaccuracies are flagged. Potential penalty based on behaviour.
How to Avoid HMRC Penalties
The good news is most penalties are avoidable with a few simple habits.
Keep records during the year
Track income and expenses as they happen. Don’t wait until the deadline.
Know your deadlines
This becomes more important under MTD, where quarterly submissions mean four deadlines a year instead of one.
Don’t ignore HMRC letters
Early action usually reduces penalties. HMRC is more lenient when you engage promptly.
Register when required
If you cross thresholds, deal with it early rather than later. The penalties for failure to notify increase with time.
Use proper tools
Digital systems help reduce missed deadlines and errors. Automated reminders and real-time tracking make a real difference.
Where 123Tax Helps
Tax penalties aren’t usually about big mistakes. They’re about small things being missed.
123Tax is built to help avoid that. By tracking income, expenses and obligations throughout the year, it becomes much easier to:
- • Stay on top of deadlines
- • Submit accurate information
- • Avoid last-minute panic
- • Reduce the risk of penalties
It’s not about doing more admin. It’s about making sure the important things don’t get missed.
Summary
HMRC penalties in 2026 will continue to apply for late filing, late payment, inaccurate returns and failure to notify.
With the introduction of Making Tax Digital for Income Tax, a new points-based penalty system will apply to missed submissions, increasing the number of potential trigger points.
The most common causes of penalties remain simple: missed deadlines, poor record-keeping and lack of awareness.
Understanding the rules and keeping basic records throughout the year significantly reduces the risk of penalties and helps ensure compliance with HMRC requirements.