In the UK, the Self-Assessment deadline for the 2024/25 tax year (6 April 2024 to 5 April 2025) is midnight on Saturday 31 January 2026. You must submit your online tax return and pay any tax owed by then to avoid penalties. The £100 late filing fine kicks in automatically if you miss it — even if you owe nothing or are due a refund.
This applies to self-employed individuals, landlords, those with untaxed income (e.g., savings interest, dividends), higher earners hit by the High Income Child Benefit Charge, and anyone HMRC has notified to file. Paper returns closed earlier (31 October 2025), so January is all about online filing via GOV.UK.
Why Deadline Day Is Always Chaotic — Especially on a Saturday
Millions wait until the final days, hours, or minutes, causing:
- Huge spikes in traffic to HMRC's online systems.
- Last-minute panic over logins, UTRs, calculations, or submission errors.
- Frustration when issues arise and support feels out of reach.
HMRC repeatedly urges early filing — you can submit from 6 April 2025 onwards, pay later (by 31 January), and skip the stress. Yet, with over 3 million still outstanding in the final weeks of January 2026, the rush is predictable.
HMRC Phone Lines: Closed on Saturday 31 January 2026
Unlike some past years when HMRC occasionally extended phone support for weekend deadlines (e.g., limited hours on a Sunday 31 January), this year there is no phone helpline available on the actual deadline day.
- Standard Self-Assessment helplines (e.g., 0300 200 3310) operate Monday to Friday, 8am to 6pm.
- They close at 6pm on Friday 30 January 2026 and don't reopen until 8am on Monday 2 February 2026.
- No weekend phone support means if you're stuck on Saturday — with login problems, verification issues, or submission errors — you can't speak to an adviser.
This is a deliberate shift: HMRC has been reducing phone reliance in recent years, closing self-assessment lines entirely for parts of the year and prioritising digital channels. On deadline Saturdays, they don't make exceptions for phone access.
What Support Is Available on 31 January 2026?
HMRC isn't leaving people completely without help:
- Enhanced webchat via the Online Services Helpdesk is available from 8am to 4pm on Saturday 31 January, with extra advisers to handle queries.
- The digital assistant ("Ask HMRC") runs 24/7 for basic guidance.
- Full online filing and payment systems remain open until 11:59pm.
But webchat isn't the same as a phone call — queues can build, and complex issues may still require follow-up after the deadline.
Tips to Survive (or Avoid) Deadline Day Chaos
- File now — With the date falling on a Saturday, aim to submit by Friday 30 January at the latest for any chance of phone help if things go wrong.
- Prepare early — Gather P60s, invoices, expense records, and check eligibility/filing requirements via HMRC's online tool.
- Use digital alternatives — HMRC app, online account, and webchat are more reliable than phones during peaks.
- If you can't pay in full — Set up a Time to Pay plan online (for debts up to £30,000) without needing to call.
- Don't rely on phones — Resolve issues well before Friday evening. If you miss the deadline, you can appeal the £100 penalty later with a "reasonable excuse" (though technical glitches or last-minute rushes rarely qualify).
HMRC's message is clear: the system rewards early action. Deadline day on a weekend, with no phone lifeline, makes waiting until the end even riskier. If you're in London or anywhere else in the UK and still haven't filed as we approach 31 January 2026 — log in to GOV.UK today, check everything twice, and hit submit. The silence on the phones will be deafening if you leave it too late.