What Happens If You Miss The Self Assessment Filing Deadline?

Filing your Self Assessment Tax Return can be a stressful task, but missing the deadline comes with serious financial consequences. If you’re running late or worried about missing the cut-off date, what happens next? ...

The deadline for online submission is midnight on the 31st of January, while paper submissions must be received by the 31st of October, three months earlier. Failing to file on time can lead to penalties, so aim to submit your return promptly. Even if you're unable to pay the full amount owed, filing your return ensures that penalties are kept to a minimum.

"If you miss the 31st of January deadline for online submissions, you will face penalties!"

Initially, there is a fixed penalty of £100 for up to three months late. After three months, daily penalties of £10 per day can accrue for up to 90 days. For returns that are six or twelve months late, additional penalties of £300 or 5% of the tax due (whichever is higher) will apply. The same penalty regime applies for paper returns submitted after the 31st of October deadline.

In addition to late filing penalties, you may also face charges for late payment of taxes owed. If payment is 30 days late, a 5% penalty of the tax due is charged. At six months, an additional 5% of the outstanding tax is applied, followed by another 5% at twelve months. Even if you can't pay the full amount immediately, making a payment as soon as possible can help reduce penalties.

"Starting in April 2026, HMRC will introduce a new points-based penalty system for late submissions!"

Each missed deadline will earn points, and reaching a certain threshold triggers a £200 fine. Subsequent late submissions will incur additional £200 fines without increasing your points total. The penalties will vary depending on whether you're required to file annually, quarterly, or monthly.

Fines can sometimes be avoided under specific circumstances. HMRC may waive penalties if you have a "reasonable excuse" such as the death of a close relative shortly before the deadline, serious illness, or technical issues with HMRC's online services. If you believe you have a valid excuse, you can appeal the penalty using form SA370 or online through HMRC's portal. However, excuses like finding the system too difficult or not receiving a reminder are not considered valid.

"To avoid future issues, file your return as early as possible!"

Once the tax year ends on the 5th of April, you can file your return anytime before the 31st of January. Keeping detailed records is essential, as you must retain them for at least five years after the relevant submission deadline.

Missing the Self Assessment deadline can be costly, but staying informed and organised can save you from unnecessary stress.

Don't wait until the last minute; file your return early and avoid surprises.

If you feel inspired to find out more about anything I've said here, do call me on 01908 774320 or leave a comment below and I'll be in touch as soon as I can.