Self Assessment Deadline: 100 Days Left as 12 Million Face 31 January Filing Rush
HM Revenue and Customs has issued a reminder that Self Assessment customers have 100 days remaining to file their tax return for the 2025 to 2026 tax year, with the deadline falling on 31 January 2027[1]. Around 12 million people are expected to submit a tax return by the deadline[1].
The announcement, published by HMRC on 23 October 2026[1], urges taxpayers to "get ahead of the January rush" and file early. Myrtle Lloyd, HMRC's Chief Customer Officer, said: "The Self Assessment deadline is 100 days away so now is the ideal time to get ahead and file your tax return early"[1].
Self Assessment applies primarily to self-employed individuals, including sole traders and partners in business partnerships, alongside others with income not taxed at source. Those who submit early can find out how much tax they owe before the deadline, give themselves more time to budget, get a refund quicker if they have paid too much tax, and avoid penalties[1].
Filing process and support
Customers can complete and file their tax return for the 2025 to 2026 year via GOV.UK[1]. Those unsure whether they need to complete Self Assessment can use the GOV.UK checker tool[1].
People who are new to Self Assessment must first register to receive their Unique Taxpayer Reference, which they will need when they complete and file their return[1]. Anyone who needs to tell HMRC that they no longer need to submit a tax return can do so on GOV.UK[1].
A range of support and guidance is available on GOV.UK, including help filling in the sections of tax returns, videos explaining how to complete returns, and HMRC's digital assistant which can answer common questions about Self Assessment[1]. Self Assessment customers can also ask a tax agent, friend or family member, or a voluntary organisation to help them[1].
Those signed up to Making Tax Digital for Income Tax still need to submit their Self Assessment tax return in their usual way and pay any tax owed by 31 January 2027[1].
Register context: UK business landscape
While HMRC's announcement does not break down the 12 million Self Assessment filers by sector, CompanyPulse data[2] provides context on the broader UK business register. Across the entire UK register, 5,432,394 companies are currently active, with 7,061,396 total companies registered[2].
The most common business activities on the UK company register - noting these figures describe all registered companies economy-wide, not Self Assessment filers specifically - are concentrated in real estate, consultancy, and technology sectors[2]. The single largest category is "Other letting and operating of own or leased real estate" with 448,779 companies, followed by "Buying and selling of own real estate" with 276,799 companies, and "Management consultancy activities other than financial management" with 276,576 companies[2].
Other significant sectors across the UK register include business support services (218,074 companies), online retail (210,635 companies), IT consultancy (166,936 companies), and software development (115,427 companies)[2]. Construction sectors are also well-represented, with 113,949 companies in building project development and 100,356 in domestic building construction[2].
In the past seven days, 15,134 new companies were incorporated across the UK[2]. Daily incorporation figures from late September through October 2026 show weekday registrations typically ranging from 2,000 to 3,500 companies per day, with the highest single day reaching 3,540 incorporations on 30 September 2026[2].
Insolvency across the register
Across the entire UK company register, 147,151 companies are currently in liquidation, 46,573 are in administration, 35,034 are in voluntary arrangements, and 631 are in receivership[2]. These economy-wide figures provide broader context for the financial pressures facing UK businesses, though they do not specifically measure Self Assessment compliance risk.
Concurrent filing reforms
The Self Assessment reminder comes as the government announced changes to how companies will file accounts with Companies House from April 2028[3]. On 23 October 2026, Companies House confirmed it will pause the introduction of small companies and micro-entities filing profit and loss accounts while the government considers alternative options to simplify filing processes[3].
During this pause, the government will explore options for streamlining Companies House and HMRC filing processes, under the 'tell Government once' ambition[3]. The government stated it remains "committed to delivering our economic crime objectives in a way that is in keeping with our wider ambitions to reduce business burdens and improve filing processes"[3].
In practical terms, this means the government will continue to allow companies to file abridged accounts and retain the option for smaller companies to remove, or 'fillet', their profit and loss information from the accounts filed at Companies House after 1 April 2028[3].
However, from April 2028, all UK registered companies will be required to file their accounts using commercial software[3]. Companies House stated that software filing will "improve the quality of financial data for register users and provide more opportunities over time for companies' accounts data to be aggregated, compared and analysed for use more widely"[3].
Outlook
With the 31 January 2027 deadline approaching, the coming 100 days will test whether HMRC's early filing campaign can reduce the traditional January rush. The announcement emphasises that submitting early allows taxpayers to identify any tax owed well in advance of the payment deadline, potentially easing cash-flow planning for the millions of self-employed individuals and business owners who must file.
The concurrent reforms to Companies House filing processes signal a broader government ambition to streamline how businesses report to different arms of the state, though the full integration of HMRC and Companies House systems remains a longer-term objective rather than an immediate change for the 2025-26 tax year.
