Self Assessment Penalties
What HMRC charges if you file or pay late, and what to do if you have already missed a deadline.
Articles
Late filing penalties
How late filing penalties build up: the £100 immediate fine, daily penalties, and 6 and 12 month escalations.
Self Assessment late payment penalties
Interest plus 5% surcharges at 30 days, 6 months, and 12 months. How to limit the damage if you cannot pay on time.
Late filing vs late payment
These are two different penalty regimes. Filing late triggers fines even if you owe nothing. Here is the difference.
What does filing late actually cost?
£100 the moment the return is late — owe tax or not. From three months late, £10 a day for up to 90 days. At six months, a further £300 or 5% of the tax due, whichever is higher; the same again at twelve months. A return filed a year late has typically accumulated £1,600 or more in filing penalties before any tax is counted.
The structure is deliberate: it punishes delay itself, which also means it rewards stopping the delay — the daily penalties stop the day you file.
Late payment runs on its own track
Interest accrues daily from the due date on any unpaid tax, automatically. At 30 days late a 5% surcharge lands on the outstanding balance, with further 5% charges at six and twelve months. Filing penalties and payment penalties stack — they are separate regimes for separate failures.
A Time to Pay arrangement, made and kept, stops the surcharges. It does not stop the interest — nothing does except payment.
Reasonable excuse: narrower than people hope
HMRC cancels penalties for a reasonable excuse: serious illness at the deadline, bereavement, a genuine system failure — events that actually prevented compliance, remedied promptly once they passed. Pressure of work, a difficult accountant handover, or not realising a return was due generally fail.
Appeals go in within 30 days, in writing, with the timeline evidenced. Honest and specific beats elaborate: penalties get cancelled for facts, not narratives.
Already late? Triage in this order
File first — today, even imperfectly, because the daily clock stops at filing and estimates can be amended. Pay what you can second, to shrink the base the surcharges bite. Arrange Time to Pay third. Appeal fourth, only where a genuine excuse exists.
What we bring to a late case is sequence and speed; what Deadline Lock brings to every other year is never running this playbook again.
Frequently asked questions
I owe no tax — surely there's no penalty for filing late?
The £100 penalty applies regardless of the tax due, and the three-, six-, and twelve-month additions follow the same rule. A nil return filed late costs real money; file on time even when nothing is owed.
How much is a return one year late?
Typically £1,600 or more in filing penalties alone — £100, up to £900 of daily penalties, and two further charges of £300-or-5% — plus payment surcharges and daily interest on any unpaid tax. Twelve months of small numbers compound into a serious one.
Will HMRC accept an appeal because my accountant let me down?
Rarely — relying on an agent is generally not a reasonable excuse, since the obligation stays yours. Exceptions exist where the failure was truly outside anyone's control. If a handover has stalled near a deadline, filing something on time beats appealing later.
Can penalties be suspended rather than cancelled?
Suspension exists for some careless-error penalties on inaccurate returns, subject to conditions — but not for late filing penalties. For lateness the only levers are reasonable excuse and stopping the clock by filing now.