HMRC letters explained
What the most common HMRC letters mean and what to do when you receive one.
The most common HMRC letters
Most HMRC letters fall into a handful of categories. Knowing which is which tells you how urgent and serious it is.
"Notice to file a tax return" (SA316)
You're being asked to file a Self Assessment. If you don't think you should be filing, contact HMRC — but the safe option is usually to file (a nil return is fine if you owe nothing).
Tax calculation (SA302) or simple assessment (PA302)
HMRC's calculation of what you owe based on returns or PAYE data. Check it against your records. If you disagree, you have 30 days to challenge it before HMRC moves to enforcement.
Penalty notice
You've been issued a penalty (late filing, late payment, inaccuracy, or another reason). The notice will say what for and how much. You have 30 days to appeal if you believe it shouldn't apply.
"We're checking your tax return" (compliance check)
HMRC is opening an enquiry into one or more of your returns. Treat this seriously — get professional advice before responding. They'll usually ask for specific records or clarification on specific figures.
"We need to know more about your business" (information notice)
A Schedule 36 notice — HMRC is formally requesting information you must provide. There are penalties for not complying. Take this very seriously and consider getting representation.
Determination or assessment
HMRC has estimated what you owe because you didn't file or didn't provide enough information. The estimate often exceeds reality. You usually have 30 days to file a proper return to displace the determination.
"Discovery assessment"
HMRC has uncovered a past underpayment they think you owe. These can go back four, six, or twenty years depending on whether they think the error was careless, deliberate, or accidental. Get professional advice immediately.
What to do when one arrives
- Read it carefully — note any deadlines
- Don't ignore it — penalties escalate fast
- Cross-check against your records
- If you disagree, gather evidence and appeal in writing within 30 days
- For complex letters (compliance checks, Schedule 36, discovery assessments), get an accountant involved straight away