Missed the Self Assessment Deadline? Penalties and Next Steps

2 min read

Table of Contents

Immediate late-filing penalty
Penalties after 3, 6 and 12 months
Late-payment penalties
What to do now
Reasonable excuse
How to appeal
What if HMRC should not have required a return?
Cannot pay the tax
Missing the registration deadline
Paper versus online deadline
Amending a late return
HMRC determinations
Deliberate non-disclosure
Preventing recurrence
Official guidance

If you miss a Self Assessment deadline, file and pay as soon as possible. Filing penalties are separate from late-payment penalties and interest, so submit the return even when you cannot pay the bill in full.

Immediate late-filing penalty

An online return filed after 31 January normally receives an automatic £100 penalty, even if no tax is due or the tax was paid on time.

Penalties after 3, 6 and 12 months

Delay	Typical additional filing penalty
More than 3 months late	£10 per day for up to 90 days, maximum £900
6 months late	5% of tax due or £300, whichever is greater
12 months late	Another 5% or £300; higher penalties can apply for deliberate withholding

These are in addition to the initial £100.

Late-payment penalties

Unpaid tax can attract penalties at:

30 days: generally 5% of tax still unpaid;
6 months: another 5%;
12 months: another 5%.

Late-payment interest runs from the original due date until payment. Payments on account can also generate interest where unpaid or reduced too far.

What to do now

Gather records and file the return immediately.
Use provisional figures where legally permitted rather than waiting indefinitely.
Pay as much as possible.
Check the HMRC statement for penalties, interest and payments on account.
Contact HMRC about Time to Pay if the balance cannot be cleared.
Appeal promptly where a genuine reasonable excuse applies.

Reasonable excuse

HMRC considers whether an unexpected event prevented compliance and whether you acted without unreasonable delay after it ended. Possible examples include serious illness, bereavement, fire, flood, unexpected HMRC system failure or postal disruption where paper filing was required.

Lack of funds, reliance on an accountant without oversight, misunderstanding the rules or pressure of work is not usually enough by itself. Evidence and a clear timeline are important.

How to appeal

Appeal online or in writing within the deadline shown, normally 30 days from the penalty notice. Identify each penalty, explain the excuse and attach evidence. File the return and pay while the appeal is considered where possible.

What if HMRC should not have required a return?

If no return was legally needed, ask HMRC to withdraw the notice to file. A successful withdrawal removes associated filing penalties. Do not assume a nil liability automatically cancels the notice.

Cannot pay the tax

A Time to Pay arrangement can spread an affordable debt. Some taxpayers can apply online within current limits; others contact HMRC. Interest normally continues, but an arrangement agreed by the relevant date can reduce late-payment penalties.

See HMRC Time to Pay guidance.

Missing the registration deadline

If you did not tell HMRC by 5 October, register immediately. Failure-to-notify penalties depend on the potential lost revenue, behaviour and disclosure. A late registration does not remove the need to file.

Paper versus online deadline

Paper returns are normally due 31 October, while online returns are due 31 January. If the paper deadline has passed, filing online by 31 January can avoid a late-return penalty where online filing is available.

Amending a late return

A return can normally be amended within 12 months of the original filing deadline. Later corrections may require an overpayment-relief claim or disclosure. Filing a provisional return does not remove the duty to replace estimates promptly.

HMRC determinations

Where no return is filed, HMRC can estimate the tax due. The determination may exceed the real liability and can be displaced only by submitting the return within the statutory window. Do not ignore it.

Deliberate non-disclosure

Deliberately hiding income can trigger tax-geared penalties, extended assessment time limits and, in serious cases, criminal investigation. Make an unprompted disclosure before HMRC contacts you where possible and obtain professional advice.