Official HMRC manual on tax adviser registration clarifies rules

Sara White, Editor, Business & Accountancy Daily. Croner.

HMRC issues first official manual MTAR10000 on mandatory tax adviser registration, offering more clarity, but still a fortnight since sign-ups started, and still confusing to understand.

From 18 May, tax advisers, accountants, and even conveyancers had to start registering for the compulsory HMRC tax adviser register with staggered sign-up dates depending on different sectors.

In the run-up to the start of the mandatory register HMRC issued piecemeal updates, but now finally it has issued a comprehensive HMRC manual MTAR10000-20000 on the compliance rules.

Essentially any adviser who ‘interacts with HMRC on behalf of their clients’ on tax related issues have to sign up to the register. However, firms with agent services accounts (ASA) will be automatically considered as on the register and will be contacted directly by HMRC to confirm they are officially registered. This means that no further action should need to be taken by these specific ASA holders.

Final registration must be completed by 31 March 2027, with different start dates for each tranche of tax advisers and peripheral firms.

Registration deadlines

Registration period	Type of tax advisers
18 May to 18 Aug 2026	New tax advisers, or those interacting with HMRC without an agent services account (ASA), self assessment or corporation tax account
18 Aug to 18 Nov 2026	Tax advisers with a self assessment or corporation tax account without an ASA
18 Nov 2026 to 18 Feb 2027	Advisers who solely provide payroll services without an ASA
31 Dec 2026 to 31 Mar 2027	Financial services organisations without an ASA

Source: HMRC Manual MTAR10000

This is a register for tax advisers, not in-house tax teams at companies and multinationals.

The HMRC manual clearly states under the section on ‘services that are not in scope of registration’: ‘An in‑house tax professional or team which prepares or files tax returns solely on behalf of their employer and does not provide tax advice or services to external clients.’

Definition of a tax adviser

For the purposes of mandatory registration, a tax adviser is defined in section 224 of Finance Act 2026 as ‘an organisation or individual which, in the course of a business, assists other persons (‘clients’) with their tax affairs’.

Individuals that are employed by the tax adviser business will not need to register, as registration is only required by the legal entity providing the services. 

The HMRC manual states: ‘The person or organisation that must register is the legal entity providing the service. Where the business is a sole trader, the legal entity will be an individual.

‘Registration is required solely in circumstances where a business:

• interacts with HMRC in relation to another person’s tax affairs;

• is paid for providing that service.

‘Assistance with a client’s tax affairs includes, but is not limited to:

• advising a client in relation to tax

• acting, or purporting to act, as agent on behalf of a client in relation to tax

• assisting with the preparation of, or providing input into, any document that HMRC is likely to rely on in determining a person’s tax position.’

It is important to note that ‘free advice or work undertaken voluntarily and without payment or receiving any benefits in kind (for example, pro bono work or assisting friends and family) are not, by themselves, treated as being provided in the course of a business,’ according to HMRC. 

While the obvious tax advisory and accountancy firms will have to register on the list, the scope is quite wide, with conveyancers pulled into the system, if they are involved in submitting stamp duty land tax (SDLT) returns for their clients.

On conveyancers, the HMRC manual states:’ Submitting an SDLT return on behalf of a client is assisting with a document that HMRC is likely to rely on to determine a person’s tax position and therefore constitutes interaction with HMRC in relation to tax.’

But note if a conveyancer merely provides advice on a property transaction but does not interact with HMRC per se it will not have to register. The catalyst is actually dealing directly with HMRC, for example by filing an SDLT return.

It is the same situation for payroll services as all professional payroll companies will have to register if they are not already an ASA holder. HMRC has come up with a definition of ‘payroll-only’.

‘For the purposes of mandatory registration, businesses are treated as “payroll-only” where they solely interact with HMRC in relation to PAYE,’ the manual states. PAYE services covers submission of real time information (RTI) returns, full payment submissions (FPS) and payment of PAYE/NICs to HMRC, and all the other related employment tax filings such as P60s and so forth.

These payroll agencies must register in their particular three-month window between 18 November 2026 and 18 February 2027.  

However, simply producing a payslip for employees with the tax calculations as part of the day to day business and HR activity will not trigger registration as long as ‘they solely interact with HMRC in relation to PAYE’.  

While HMRC has attempted to make the manual accessible, these rules are hugely complicated, and seem to be excessively prescriptive with a lot of scope for HMRC to claim breaches of the rules.

This is particularly important when it comes to potential grey areas, where there may be questions over whether registration is required due to the nature of the firm’s work. HMRC defines this as ‘mixed activity’ and ‘edge cases’, the latter a phrase which has started to appear more frequently in HMRC guidance.

The HMRC manual states: ‘Where a business provides services that are caught and other services in-scope of the legislation, they will be required to register with HMRC.

‘A business cannot rely on an exception for part of its activity to avoid registration where other activities meet the legal requirement. HMRC will continue to work with the sector on more complex scenarios.’

Remember there is a penalty regime for failure to sign the register with fines of up to £5-10,000 depending on the scale of the breach and also restrictions on practice.

Useful links

HMRC manual MTAR10000, Mandatory Tax Adviser Registration [Issued 1 June 2026]