Missed the Self-Assessment deadline? Here is what you need to know for 2026

The 31 January deadline for Self-Assessment has passed, and for the 1.1 million people who missed it, the financial repercussions are now in full swing. 

HM Revenue and Customs (HMRC) has confirmed that late filers will face an automatic £100 penalty.  

However, the charges do not stop there. 

Fines and interest will continue to mount the longer your tax return remains unsubmitted. 

This serves as a warning: leaving your tax return to the last minute can cost you far more than you expect.  

This year alone, over 31,000 taxpayers filed their returns in the final hour, creating unnecessary stress and confusion. 

Penalties for late submission and payment 

So, what happens if you file or pay late? The following penalties will apply: 

• £100 fixed penalty – Applies automatically for missing the deadline, even if no tax is owed. 

• £10 per day – This penalty starts three months after the deadline, accumulating up to £900. 

• Five per cent of tax due (or £300) – If your return is six months late. 

• Additional five per cent – A further penalty applies when your return is twelve months late. 

If you owe tax and do not pay by the deadline, interest and further fines kick in: 

• Interest charges – Starts accruing on 1 February at 7.25 per cent (Bank of England base rate plus 2.5 per cent). 

• Interest rate increase – From 6 April 2025, the rate will rise to four per cent above the Bank of England base rate. 

• Late payment penalties – A five per cent penalty applies if tax is unpaid after 30 days, with further penalties after six and 12 months. 

Key takeaways from this year 

This year, a banking failure at Barclays created more stress for last-minute filers, affecting payments right before the deadline.  

Barclays has assured customers that they will not lose out financially, but this highlights the risks of waiting until the last minute. 

Unexpected issues, such as banking errors or personal emergencies, can easily prevent timely submissions.  

Early filing is the best way to avoid unnecessary penalties and stress. 

Preparing for next year’s Self-Assessment 

If you missed the 31 January deadline, don’t repeat the same mistakes next year. Here is how to stay ahead of the curve: 

• Stay organised – Keep records up to date, including invoices and receipts, so everything is ready when you need it. 

• Set your own deadline – Aim to complete your tax return well before the 31 January deadline, leaving room for any last-minute complications. 

• Get professional help – Our tax accountants can help you file correctly, identify opportunities for tax savings, and handle the paperwork with HMRC on your behalf. 

• Budget for your tax bill – be prepared financially by setting aside funds to cover your tax liability ahead of time. 

If you missed this year’s deadline, take action now to minimise the damage.  

Don’t wait until the last minute, let us help you prepare for next year’s filing and avoid the stress that comes with it. 

We are here to help you with your Self-Assessment and ensure everything is submitted on time. Contact us now to get started and take control of your tax obligations for 2026.