1. Confirm the year and the reason for filing
This guide concerns 6 April 2025 to 5 April 2026. GOV.UK says people who need a return and have not filed before, or did not need a 2024/25 return, should have notified HMRC by 5 October 2026. If that applies, take action now rather than waiting until January.
Start with our filing-requirements guide and the official registration checker. Receiving income outside payroll does not mean every person uses the same reporting route. If HMRC has issued a notice to file, address that notice even if you believe no tax is due. Seek confirmation from HMRC if you believe it should be withdrawn.
2. Register or reactivate, and keep the evidence
Use the official GOV.UK registration service. The route depends on your circumstances, including whether you are self-employed. Someone returning to Self Assessment may need to reactivate an existing account. Locate any existing Unique Taxpayer Reference and previous correspondence before starting.
Keep the submission confirmation, registration date and copies of messages. If you have already applied and are waiting for a UTR, follow the response-time checker linked by GOV.UK. Record follow-up attempts and outstanding requests. Appointing an adviser and authorising them to act are separate practical steps to arrange early.
3. Keep filing and payment dates separate
The normal online filing date for 2025/26 is 31 January 2027. For registration after 5 October 2026, current GOV.UK guidance says HMRC will provide a filing deadline three months from the date of its letter or email. Read the actual notice and retain it with your records.
That does not automatically extend payment: GOV.UK says tax must still be paid by 31 January 2027. Do not assume a later filing date also gives you longer to fund the bill. Where a notice or an unusual circumstance appears inconsistent with the standard guidance, have the specific position checked.
4. Understand what each penalty relates to
A failure-to-notify penalty concerns not telling HMRC when required. GOV.UK explains that registering after 5 October and leaving tax unpaid after 31 January can result in this penalty, calculated by reference to unpaid tax. Late filing is a different failure, with an initial £100 penalty when a required return misses its filing deadline.
Late payment can also attract penalties and interest. Do not treat these as one automatic registration fine or assume paying tax removes an existing filing obligation. If a penalty arrives, check its reason, relevant dates and calculation before deciding whether there are grounds to challenge it.
5. Prepare the figures while the account is being set up
Create a one-page schedule of each income source, the period covered, gross receipts, tax already deducted and missing documents. For a new trade, identify the start date and gather sales and expense records. For property, reconcile rent and agent deductions. Include employment, savings, dividends, overseas income and disposals where relevant so the calculation is complete.
Use our records checklist and payments-on-account guide. The amount needed in January may include a payment towards the following year as well as the completed-year balance. Agree how to calculate and pay the liability if registration is still pending; do not guess a payment reference.
6. Flag earlier years separately
If the same income began before 6 April 2025, identify every affected year and any returns already submitted. Registering for 2025/26 alone does not resolve earlier omissions. The correct route may involve an amendment or a separate disclosure, depending on the year and facts.
Give an adviser the full chronology, including HMRC contact and previous advice. Keep the underlying evidence and avoid submitting an incomplete account simply to close the registration task.
Get the registration and return moving together
UA Tax assists first-time and returning filers in London and across the UK. Personal tax services start from £400. Earlier-year disclosures, complex reconstructions and specialist advice may need a separate scope.
Get in touch with the tax year, income sources, whether you have a UTR and any HMRC deadline. We will confirm the work, fee and delivery timetable after reviewing the information. Please use the secure route we arrange for identity documents and detailed financial records.
For advice on your own circumstances, see our Self Assessment registration service and agree the scope before acting.
Official sources and further reading
These primary sources support the framework above. Check the current version before acting because tax law and HMRC guidance can change.