Personal Tax Penalty Calculator, 2026/27
Paying your self-assessment bill late triggers separate penalties from late filing, plus daily interest. This calculator estimates the late payment penalty and interest charge for directors and sole traders who have missed the 31 January deadline.
The personal tax penalty calculator runs on the rates and thresholds HMRC has published for the 2026/27 tax year, so the figures you see reflect the position your company is actually filing on rather than a historic set of bands. Change any input and the result recalculates immediately, with no sign-up and nothing sent anywhere.
If you are a director of a UK limited company, use it as a first look before a decision rather than as the decision itself. Late payment penalties: 5% of unpaid tax at 30 days late, a further 5% at 6 months, and a further 5% at 12 months. Real company positions bring in other income, reliefs, group structures and prior year adjustments that a single page of inputs cannot see, which is why the workings are written out below under personal & self assessment tax. Read those, then check the numbers against your own accounts, and speak to us if anything looks materially different from what you expected.
Last reviewed 12 September 2026 for the 2026/27 tax year. Reviewed by Waqas Sagar, Member of ICAEW, Fellow of ACCA, Fellow of AAT.
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Result, 2026/27
Total penalties and interest
Late payment penalties
5.0% of the unpaid taxInterest accrued
7.8% annual rate, daily basisTax still outstanding
Illustration only, figures are based on the rates you have selected and the information entered. Please check your own position with us before acting.
Estimates for the 2026/27 tax year using published GOV.UK rates. Switch between 2026/27 and 2025/26 above.
How this is calculated
This is specifically the penalty regime for paying tax late, separate from the penalty for filing a return late. A first penalty of 5% of the unpaid tax applies once payment is 30 days overdue. A further 5% is added at 6 months, and another 5% at 12 months, so unpaid tax outstanding for a full year can attract penalties of 15% on top of the original bill.
On top of penalties, HMRC charges interest on unpaid tax from the original due date until it is paid, currently 7.8% a year, calculated daily. This calculator applies a simple daily proportion of that annual rate to the number of days late you enter.
Interest and penalties are calculated on different bases and both apply together, so the total shown here combines the two.
Late payment versus late filing
This calculator only covers penalties for paying late. A separate, and often larger, set of penalties applies for filing the return itself late, starting at a fixed £100 even if there is no tax to pay, which is covered by the self-assessment penalty calculator elsewhere on this site.
It is possible to file on time but pay late, or vice versa, and each triggers its own penalty track independently.
Avoiding or reducing penalties
Contacting HMRC before the deadline to arrange a Time to Pay agreement can prevent the 30-day late payment penalty from being charged at all, provided the agreed instalments are then kept to. Interest still runs on any balance outstanding under such an arrangement.
A reasonable excuse, such as a serious illness or bereavement close to the deadline, can sometimes get a penalty cancelled on appeal, but this needs to be argued with HMRC directly and is judged case by case.
What this means for your company
Treat the result as a planning figure for the 2026/27 tax year. If it changes what you were about to do, take a director's salary, a dividend, a large asset purchase or a filing decision, check it against your own accounts first. We can review the position with you and confirm the tax treatment before you commit.
Frequently asked questions
When does the first late payment penalty apply?
Once tax is 30 days overdue from the payment deadline, a penalty of 5% of the unpaid amount is charged, followed by further 5% penalties at 6 and 12 months if the tax remains unpaid.
Does interest apply as well as the penalty?
Yes. HMRC charges daily interest on unpaid tax from the due date regardless of penalties, and the two run alongside each other rather than one replacing the other.
Can I avoid the penalty by arranging Time to Pay?
Setting up a Time to Pay arrangement with HMRC before the 30-day point can avoid the first late payment penalty, though interest continues to accrue on the outstanding balance.
Is this the same as the late filing penalty?
No. Late filing penalties apply for submitting the return itself late and start at a fixed £100, independently of whether the tax was paid on time.
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