Personal Tax Penalty Calculator, 2026/27

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.

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.