Still Not Filed? The Costly CGT Mistake Many Taxpayers Make Before 31 January

With the 31 January Self Assessment deadline fast approaching, it’s easy to feel overwhelmed — especially if you’ve sold property or other assets over the past year. You might be thinking, “I’ll get to it later”, or assuming that CGT doesn’t apply to you.

The truth is, understanding your Capital Gains Tax position is crucial. Today's blog explores why this is the case...

Millions Still Risk Missing the Self Assessment Deadline — Is Your CGT in Order?

It’s January, the fairy lights are down, the mince pies are long gone, and yet… millions of taxpayers are still staring at a blank Self Assessment form. If you’ve sold property, shares, or other assets, your Capital Gains Tax (CGT) obligations aren’t going to file themselves — it's time to step away from the tin of Roses and get things ticked off your 'To Do' list.

According to HMRC, over 6.36 million taxpayers have already filed their 2024–25 Self Assessment returns. But a staggering 5.65 million people are still yet to submit theirs. That’s right — nearly half of all taxpayers are waiting until the last few weeks to hit “submit.”

Some go for the early-bird approach, like the 54,053 taxpayers who welcomed 2026 by filing their returns on New Year’s Eve and New Year’s Day. Extra keen? 342 people even submitted their returns in the final hour before midnight on NYE, making sure their tax affairs were in order before the fireworks went off. HMRC reported the most popular filing time was 11am to 11:59am on NYE, with 3,927 returns submitted in that window — we're slightly undecided about how we feel about that level of productivity.

Now, this is where the plot thickens for anyone who’s sold assets. Whether it’s a UK property, overseas property, or investments, CGT isn’t something to leave until the last minute. Miscalculating your gain, forgetting allowable costs or reliefs, or missing the 60-day property reporting window can quickly turn your “easy filing” into a stressful scramble — and yes, penalties apply.

Even a late filing £100 fine is just the tip of the iceberg. The longer you delay, the steeper the penalties, and before you know it, your tax headache could outshine the hangover from New Year’s Eve.

Picture this: it’s 11:59pm on 30 January, and you’re frantically trying to calculate a gain on a property you sold months ago. The clock ticks. The system slows. And somewhere, a very smug HMRC inspector is quietly watching your late submission roll in. It doesn’t have to be like that. Understanding your CGT liability early ensures you file accurately, avoid unnecessary tax, and — most importantly — start the year stress-free.

At The Tax Faculty, we guide both UK and non-UK clients through every twist and turn of Capital Gains Tax. We make sure your returns are accurate, reliefs and exemptions are claimed, and deadlines are met — so you can celebrate New Year 2027 without a tax form in hand.

Don’t wait until the final hour. Contact us today for a free consultation and make sure your CGT is sorted well in advance.

📧 info@capitalgainstax.co.uk

📞 0800 0016 878

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Mince Pies, Fireworks and HMRC Filing