Midnight on 31 January 2027 is three deadlines at once. It is the filing date for the 2025 to 2026 online return, the date the balancing payment for that year is due, and the date the first payment on account for 2026 to 2027 is due. Missing the filing date and missing the payment date are charged separately, which is why filing on time still matters when you cannot pay.
What the date covers
| Due on 31 January 2027 | What it is |
|---|---|
| 2025 to 2026 online return | The return for the year ended 5 April 2026 |
| Balancing payment | Tax for 2025 to 2026 less any payments on account already made |
| First payment on account | Normally half of the 2025 to 2026 tax, towards 2026 to 2027 |
The paper deadline was 31 October 2026, so from 1 November a paper return is already late even though the online date has not passed. If you registered for Self Assessment after 5 October 2026, HMRC will have written to you with a filing deadline three months from the date of its letter, but the payment date is still 31 January 2027.
Late filing penalties
| How late | Penalty |
|---|---|
| One day late | £100, whether or not any tax is due |
| Three months late | £10 a day, up to a maximum of £900 |
| Six months late | A further 5% of the tax due, or £300, whichever is greater |
| Twelve months late | Another 5% of the tax due, or £300, whichever is greater |
The £100 is automatic and applies even where the return shows no tax to pay, which surprises people who file late believing there is nothing at stake. The charges are cumulative, so a return filed thirteen months late carries the £100, up to £900 of daily penalties and two further charges of at least £300 each.
Late payment penalties and interest
| How late | Charge |
|---|---|
| Tax unpaid 30 days after the due date | 5% of the amount outstanding |
| Still unpaid at six months | A further 5% |
| Still unpaid at twelve months | A further 5% |
| Interest, from the day after the due date | 7.75% from 9 January 2026 |
Late payment interest is set at the Bank of England base rate plus four percentage points and runs from the day after the payment was due until it is paid. It applies on top of any penalty, and it applies to the penalties themselves if those go unpaid. Interest is not a penalty and is not cancelled on appeal in the way a penalty can be.
If you are in Making Tax Digital, the payment rules differ. A different late payment regime applies to people required to use Making Tax Digital for Income Tax, from the tax year they join. Nothing is charged in the first fifteen days, then 3% of the tax outstanding at day fifteen for the 2026 to 2027 year, a further 3% of what is outstanding at day thirty, and an additional 10% a year accruing daily from day thirty one. For 2027 to 2028 the two percentages rise to 4%. Late submission moves to a points system, with a £200 penalty at four points. The 2025 to 2026 return due on 31 January 2027 falls under the rules in the tables above, because that year precedes the first Making Tax Digital year.
If you cannot pay
File the return anyway. The filing penalty and the payment penalty are separate, so filing on time removes one of the two problems entirely, and until the return is filed nobody knows what the debt actually is.
Then talk to HMRC about a payment plan. HMRC can agree to instalments where it is satisfied the plan is affordable, and arrangements are available for Self Assessment debts. Agreeing a plan does not stop interest running, but it can prevent further late payment penalties while the plan is being kept to. There is an online service for setting up a Self Assessment payment plan, and eligibility is checked as part of it, so it is worth trying the online route before phoning.
What does not work is silence. A debt left alone attracts the penalties at thirty days, six months and twelve months, interest throughout, and eventually collection action.
Would you rather not do it yourself?
We prepare and file Self Assessment returns for sole traders, landlords, freelancers and directors on a fixed fee agreed before we start.
Self Assessment tax returnsAppealing a penalty
A penalty can be appealed if you had a reasonable excuse for the failure and you put things right without unreasonable delay once the excuse ended. Serious illness, a bereavement, a fire or flood, an unexpected hospital stay, a failure of HMRC's own service or problems with postal delays have all been accepted in the right circumstances. Pressure of work, a shortage of funds, not understanding the obligation and relying on someone else to do it for you have generally not.
Appeals are normally made within thirty days of the penalty notice, using the form or the online route HMRC specifies. A reasonable excuse appeal is about the facts, so set out what happened and when, and the chronology matters more than the explanation.
Correcting a return you have already filed
If you spot an error after filing, you can amend the 2025 to 2026 return yourself until 31 January 2028, which is twelve months after the filing deadline. An amendment is made in the same place you filed, and the tax is recalculated. Interest runs from the original due date on any extra tax, so an amendment that increases the bill is better made sooner.
After the amendment window closes you are into a claim for overpayment relief, which has a four year limit from the end of the tax year, or into correspondence with HMRC if more tax is due. If you realise you have underpaid, telling HMRC before it asks is considerably better for the penalty position than waiting to be found.
Dates to put in the diary now
- 31 October 2026. Paper return deadline for 2025 to 2026.
- 30 December 2026. Last date to file online and ask for the tax to be collected through your PAYE code, if you are eligible.
- 31 January 2027. Online return, balancing payment and first payment on account.
- 2 March 2027. Thirty days after the payment date, when the first 5% late payment penalty arises on tax still unpaid.
- 31 July 2027. Second payment on account for 2026 to 2027.
- 31 January 2028. Last date to amend the 2025 to 2026 return.
Official guidance referred to
- Self Assessment tax returns: deadlines
- Self Assessment tax returns: penalties
- HMRC interest rates for late and early payments
- Penalties for Making Tax Digital for Income Tax
- If you cannot pay your tax bill on time
Written by Ahmad Akhtar, Founder, Tax Mesh Ltd. Published 12 October 2026. This article is general information about UK tax and is not advice for your own circumstances. Rates, thresholds and deadlines change, so check the GOV.UK pages above or ask us before you act on it.
