Mandatory registration as a tax adviser moves into second stage

The first stage of HMRC’s mandatory registration programme for tax advisers ended in August. The second stage is now open. Tax advisers with a Self Assessment or Corporation Tax account, but without an Agent Services Account (ASA), must apply to register by 17 November 2026.

Mandatory registration of tax advisers with HMRC

Finance Act 2026 included legislation to prohibit tax advisers from interacting “with HMRC in relation to the tax affairs of a client” unless they are registered with HMRC.

An earlier article discussed HMRC’s initial high-level guidance on who needs to register, exemptions from registration and the conditions registered advisers must meet. Since then, a new registration date for financial services organisations has been confirmed, and a new HMRC manual with more detailed guidance has been published (discussed below). 

When do you need to register?

Registration is being rolled out in stages through a new online registration system for the ASA which opened on 18 May 2026. The deadlines for individual advisers and firms vary according to their circumstances. The timetable is summarised below. You can use HMRC’s online interactive tool to check if and when you need to register. 

The tool gives advisers their registration date, based on information they provide, but they then have a three-month ‘registration window’ from that date to submit their application. Where an adviser has applied within that window, they can continue to interact with HMRC while HMRC is processing the application.

First stage: Registration date 18 May 2026 (deadline for applications 17 August 2026)

New tax advisers, or those interacting with HMRC without having an ASA or accounts for Self Assessment or Corporation Tax. 

Second stage: Registration date 18 August 2026 (deadline for applications 17 November 2026)

Tax advisers with a Self Assessment or Corporation Tax account, but without an ASA. 

Third stage: Registration date 18 November 2026 (deadline for applications 17 February 2027)

Advisers who solely provide payroll services and who don’t have an ASA.

Fourth stage – registration date 31 December 2026 (deadline for applications 31 March 2027)

Financial services organisations without an ASA.

Advisers who already have an ASA

HMRC intends to transfer existing ASAs to the new system. As part of that process HMRC will check that advisers meet the registration conditions. The online guidance tool notes that HMRC will “contact you through your agent services account when we need more information”. However, we don’t yet have full details from HMRC about how the transition process will work, or the timing. 

HMRC guidance

In addition to the interactive online guidance tool, HMRC has now published its Mandatory Tax Adviser Registration manual to provide more detailed guidance on all aspects of registration. The manual is still being developed and expanded but already addresses some of the queries and issues raised by ICAS and other professional bodies in discussions with HMRC. For example, MTAR10200 considers groups and complex business structures.

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