Households across the United Kingdom are being warned of an imminent £100 fine from HM Revenue and Customs (HMRC) if they fail to meet a critical deadline this weekend. The penalty will be issued automatically from Sunday, February 1, 2026, for those who have not submitted their Self Assessment tax returns.
Immediate Penalties for Late Filing
The deadline for filing and paying Self Assessment tax returns is set for 11:59pm on Saturday, January 31, 2026. According to HMRC, an estimated 3.3 million tax returns remain outstanding, despite 8.6 million people having already filed for the 2024 to 2025 tax year. Those who miss the deadline will incur an automatic £100 late filing penalty, applicable even if there is no tax to pay or if the tax due is paid on time.
Escalating Fines Over Time
If the tax return is not filed within three months of the deadline, additional penalties of £10 per day will be imposed, up to a maximum of £900. After six months, a further penalty of 5% of the tax due or £300—whichever is higher—will be added. This increases again after 12 months with another 5% or £300 penalty. Unpaid tax will also accrue interest on the owed amount, compounding the financial burden.
HMRC Support and Deadlines
HMRC is urging taxpayers not to wait until the last minute, as this year's deadline falls on a Saturday. Phone lines will close at 6pm on Friday, January 30, and will not reopen until 8am on Monday, February 2, after the deadline has passed. On Saturday, only webchat assistance through HMRC's Online Services Helpdesk will be available for those needing help to submit their return.
Myrtle Lloyd, HMRC’s Chief Customer Officer, advised: "Don’t leave it until deadline day. Filing now will give you peace of mind that your tax return is completed and if you have tax to pay, you have a week to arrange payment."
Reasonable Excuses and Payment Plans
HMRC will consider reasonable excuses for missing the deadline on an individual basis. Acceptable reasons include:
- Death of a partner or close relative shortly before the deadline
- Unexpected hospital stays preventing tax affairs management
- Serious or life-threatening illnesses
- Computer or software failures during online return preparation
- Service issues with HMRC online services
- Fires, floods, or thefts disrupting tax return completion
- Unforeseen postal delays
- Delays related to a disability or mental illness
- Unawareness or misunderstanding of legal obligations
- Reliance on someone else who failed to send the return
Taxpayers must submit their return or payment as soon as possible after the excuse is resolved. Blaming bounced cheques, failed payments, or lack of reminders from HMRC is not considered valid.
For those unable to pay their tax bill in full by the deadline, HMRC offers an online 'Time to Pay' system to spread the cost. Eligibility requires filing the Self Assessment tax return first. Individuals owing less than £30,000 can apply online without contacting HMRC directly, while those owing more must contact HMRC to arrange a plan.
HMRC emphasised: "You must submit your online tax return by 11:59pm on 31 January 2026 or you’ll get a late filing penalty. If you want to pay your Self Assessment bill through your tax code, you must submit it by 11:59pm on 30 December 2025. If you miss this deadline, you’ll have to pay another way." Tax returns can be submitted any time from April 6, 2025, up to the deadline.
