Late filing penalties
The online deadline for 2025/26 returns is 31 January 2027. Miss it and HMRC charges:
- £100 straight away, even if you owe nothing.
- After 3 months: £10 a day for up to 90 days, a maximum of £900.
- After 6 months: 5% of the tax due or £300, whichever is greater.
- After 12 months: another 5% or £300, whichever is greater. In serious cases of deliberately withheld information it can be higher.
So a return filed 6 months late costs at least £1,300 in filing penalties alone, before any tax or interest.
Late payment penalties
Tax for 2025/26 must be paid by 31 January 2027. If it isn't, HMRC adds:
- 5% of the unpaid tax at 30 days late
- a further 5% at 6 months
- a further 5% at 12 months
Setting up a Time to Pay arrangement before a penalty date can stop the next late payment penalty being charged.
Interest
Interest runs from the day after the deadline until you pay. From 6 April 2025 it's set at the Bank of England base rate plus 4%, so it moves whenever the base rate does. The calculator uses a simple estimate; HMRC charges it daily.
Reasonable excuse and appeals
If something genuinely stopped you filing or paying on time, such as serious illness, a close family bereavement, or a problem with HMRC's online services, you can appeal. You need to have filed or paid as soon as the problem was resolved. Not having the money or not knowing about the deadline usually aren't accepted.
What to do if you've already missed the deadline
- File your return as soon as you can. The daily penalties stop once it's in.
- Pay what you can now to reduce interest and avoid the next 5% charge.
- If you can't pay it all, contact HMRC about a payment plan.
TaxGo gets your return ready in one sitting, so you can stop the clock today.