HM Revenue and Customs (HMRC) has warned households that anyone new to Self Assessment must notify the tax office by Monday, October 5, or risk incurring a penalty. The deadline for submitting a tax return and paying any tax owed for the 2025 to 2026 year remains January 31, 2027, but those with income to declare who are not already registered for Self Assessment must register first.
Registration deadline and online improvements
HMRC said it has improved its online service to make it easier for people to register, with more than 640,000 customers doing so in the 12 months to March 31, 2026. The improved system allows first-time registrants to sign up quickly through their Personal Tax Account, where forms are pre-populated with their information and details can be saved and returned to if needed.
Customers should receive a confirmation email or text once registration is complete and will be issued with a Unique Taxpayer Reference within 72 hours so they can start their return.
What happens if you miss the deadline
If you register after the October 5 deadline, HMRC will send you a letter or email with a different deadline to send your tax return by. This will be three months from the date on the letter or email. But you must still pay the tax you owe by 11.59pm on January 31, 2027, or you’ll get a penalty.
HMRC said: “If you register after 5 October and do not pay all of your tax bill by 31 January, you may get a ‘failure to notify’ penalty.
“This penalty is based on the amount still left to pay and you’ll receive it within 12 months after HMRC receives your Self Assessment tax return.”
Who needs to send a tax return
You must send a tax return to HMRC if, in the last tax year from April 6 to April 5, any of the following applied: you were self-employed as a ‘sole trader’ and earned more than £1,000 (before taking off anything you can claim tax relief on); you were a partner in a business partnership; you had to pay Capital Gains Tax when you sold or ‘disposed of’ something that increased in value; you had to pay the High Income Child Benefit Charge and do not pay it through PAYE; or you are an off-payroll worker who is repaying a student or postgraduate loan.
You may also need to send a tax return if you have any untaxed income, such as money from renting out property, tips and commission, savings interest, dividends or foreign income.
Myrtle Lloyd, HMRC’s Chief Customer Officer, said: “Anyone new to Self Assessment may not realise they need to register before they can submit their tax return.
“Registering is quicker and easier than ever. And if you register now, you’ll get your Unique Taxpayer Reference so you can start completing your return with plenty of time before the 31 January deadline.”
If you no longer need to complete a tax return you must notify HMRC as soon as possible, otherwise a return will be expected and a penalty for non-submission will be issued. Customers who are already registered for Self Assessment but didn’t submit a tax return for the 2024 to 2025 tax year will need to reactivate their account if they need to submit one for the 2025 to 2026 tax year.
