HM Revenue and Customs (HMRC) has updated its technical guidance for staff and tax professionals as the deadline for new taxpayers to register for Self Assessment approaches.
The update to the Self Assessment Manual, published on 10 September 2026, follows the launch of a new, streamlined digital registration service on 9 September. The timing is critical for individuals who need to report income for the 2025/26 tax year, as the legal deadline to register with HMRC is 5 October 2026.
Failure to register by this date can result in penalties, particularly if it leads to a delay in paying tax owed. The registration requirement applies to taxpayers who need to report income for the 2025 to 2026 tax year.
Key deadlines for the 2025/26 tax year
Taxpayers are operating within a strict window for the current filing cycle. While the registration deadline is the first hurdle, several other dates are fixed in the calendar:
- 5 October 2026: Deadline to register for Self Assessment for the 2025/26 tax year.
- 31 October 2026: Deadline for submitting paper tax returns.
- 31 January 2027: Deadline for submitting online tax returns and paying any tax due.
The revised Self Assessment Manual provides the procedural framework for how HMRC handles these returns, including the processing of repayments and the application of late-filing penalties. The 10 September update ensures the manual reflects the most recent internal processing standards and the capabilities of the new digital registration portal.
The shift to Making Tax Digital
The current filing cycle is also the first to be affected by the full implementation of Making Tax Digital (MTD) for Income Tax, which became active on 6 April 2026. This mandatory change applies to sole traders and landlords with a qualifying income of more than £50,000.
Under these rules, eligible taxpayers must keep digital records and use MTD-compatible software to send quarterly updates to HMRC, rather than relying solely on a single annual return. However, for those with income below this threshold, the traditional Self Assessment process remains the standard method for reporting tax.
Taxpayers who are unsure of their status are encouraged to use the improved online service to check if they need to send a return. HMRC has stated that the new system is designed to simplify the “onboarding” process for those entering the tax system for the first time or returning after a break in self-employment.
While the Self Assessment Manual is primarily a technical document for HMRC officers, it is also used by accountants and tax advisers to ensure compliance with national standards. The latest version reflects the government’s continued move toward a fully digital tax administration, while maintaining the traditional deadlines for paper filings for those who are exempt from digital requirements.
