Mandatory registration of tax advisers with HMRC

Since 18 May 2026 a business that is paid to deal with HMRC about someone else’s tax affairs must be registered with HMRC before it does so, unless a statutory exception applies. Registration is made by applying for an agent services account, and the business and its senior people must meet registration conditions on their own tax affairs, conduct and AML supervision for as long as they stay registered.

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What does the law actually prohibit?

Section 223 of the Finance Act 2026 says a tax adviser may not interact with HMRC in relation to the tax affairs of a client unless the adviser is registered, or an exception in Schedule 20 applies. “Interact” is drawn very widely. It covers contacting HMRC by telephone, post or email, sending a message through a website or portal, filing a return, claim, notice or other document, and communicating with HMRC in any other way. HMRC’s guidance adds making payments and messages through the HMRC app.

The prohibition applies even if the adviser or client is outside the UK, and an employee’s interaction is treated as made by the firm. That is why the registering person is always the legal entity, not the individual staff members.

For the mechanics of applying and of client authorisation, see HMRC agent services account and authorising an agent.

Who counts as a tax adviser?

Section 224 defines a tax adviser as a person who, in the course of a business, assists other people with their tax affairs. That includes acting as agent on a client’s behalf, and helping to prepare or providing input into any document HMRC is likely to rely on to decide someone’s tax position. HMRC’s manual at MTAR10150 reduces the test to three conditions, all of which must be met:

the business acts as a tax adviser or otherwise assists a client with their tax affairs;
it interacts with HMRC in that capacity; and
it does so in the course of business.

“In the course of business” means work connected to a commercial or professional activity in exchange for payment, including payment in money’s worth (MTAR10100). Genuinely free help to friends and family is outside the rules, but HMRC is clear that doing some unpaid work as part of a business’s services does not remove the requirement. Registration is needed even if the business does not see itself as a tax adviser or acts for only one client.

What about subcontractors and specialists?

MTAR10150 looks at the practical reality of who is acting for the client. Where a firm engages another party to help, for example to attend a meeting with HMRC, but the interaction happens under the authority and control of the principal adviser, the interaction is treated as made by that principal firm. Where the subcontractor takes responsibility for communicating with HMRC, or presents itself as the person acting for the client, it must register in its own right. Outsourcing arrangements therefore need to be clear about which business is the client’s agent.

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Which activities are exempt?

Only the exceptions in Schedule 20 have statutory effect. MTAR10300 lists businesses that solely do one or more of the following: provide tax or accounting software (including payroll software); act on customs duty, import VAT or excise; act as a VAT representative, Northern Ireland tax representative, UK representative for vaping duty or Import One Stop Shop intermediary; advise other entities in the same group; act in appeals to a court or tribunal; interact with HMRC because the law requires it (such as insolvency practitioners); or respond to an HMRC request for information. Business rates, council tax and property valuation services are also outside the rules.

The key word is “solely”. MTAR10300 states that a business cannot rely on an exception for part of its activity to avoid registration where other activities meet the requirement.

When does a business have to be registered by?

Registration has been phased in by tranches, each with a three month window (MTAR10800). New advisers and those dealing with HMRC without an agent services account, Self Assessment or Corporation Tax agent account were due between 18 May and 17 August 2026. Firms with a Self Assessment or Corporation Tax agent account but no agent services account have until 17 November 2026. Businesses that solely provide payroll services follow from 18 November 2026, and financial services organisations from 31 December 2026. A firm that offers payroll alongside tax or accounts work falls into the earlier tranche.

A business can keep interacting with HMRC during its window and while an application made in time is processed. HMRC now tells anyone who missed their window, or is new to the market, to register now, so a new practice should complete registration before it first contacts HMRC for a client.

What conditions must the business meet?

Section 227 sets the registration conditions, which HMRC summarises at MTAR20200. The business must not:

have relevant outstanding returns or unpaid tax, unless covered by an agreed Time to Pay arrangement;
be subject to an HMRC decision refusing to deal with it;
be subject to an anti avoidance sanction or stop notice, or an anti avoidance penalty in the last 12 months;
be disqualified from acting as a director;
have relevant unspent convictions for fraud or tax offences;
have an insolvency practitioner acting in relation to it; or
be suspended or permanently banned from registering.

The business must also provide evidence of AML supervision. MTAR20200 says that having applied for supervision is not accepted, so a new firm must have its supervisor’s approval before it applies. See AML supervision for accountants.

The overdue returns test has detail of its own (MTAR20300). HMRC checks only the adviser’s own tax affairs, not returns filed for clients. A return position fails where the equivalent of one year’s worth of required returns is still outstanding after a grace period: one annual return for Corporation Tax or Income Tax, or a year’s worth of quarterly VAT returns. Amounts under genuine dispute are not treated as overdue, and a Time to Pay arrangement only protects the position while it is being kept to.

Who are relevant individuals and what do they have to do?

Under section 226 a relevant individual is someone working for the adviser who plays a significant role in deciding how all or a substantial part of its tax advice activities are managed, or in actually managing them. MTAR20400 stresses that the test is about substance, not job title, and that staff whose only role is day to day client work are not intended to be caught. Where a business has fewer than six officers (directors, partners, LLP members and overseas equivalents), the legislation treats every officer as a relevant individual. A firm with six or more officers identifies those with real strategic or managerial control and must nominate more officers if fewer than five meet the definition.

Relevant individuals face identity, criminality, insolvency and personal tax checks (MTAR20500), but they are not personally responsible for clients’ affairs. From April 2027, when the transitional period ends, firms must tell HMRC when a relevant individual joins, leaves or changes role. Existing account holders will be contacted in early 2027 for these details (MTAR20200).

What happens if a condition stops being met?

Registration is ongoing, so a lapse after registration can lead to suspension under section 232. HMRC must first give notice and a period to fix the problem or make representations: 30 days in most cases, extended to 60 days where the issue is an overdue amount or outstanding return (MTAR30200). A suspension for failing a condition lasts until HMRC is satisfied the condition is met again. During suspension the firm loses access to its agent services account and cannot deal with HMRC for clients by any channel, although it can still deal with HMRC about its own taxes.

If a suspension lasts more than 30 days, section 238 requires the firm to notify its clients within 30 days beginning with the 31st day. HMRC may charge £5,000 for each client not told (MTAR30550). Interacting while unregistered or suspended leads to a compliance notice, then penalties and bans, which are set out in our page on the HMRC standard for agents.

Can a suspension be challenged?

Refusal, suspension, compliance notices, penalties and ineligibility orders are appealable under Schedule 21. HMRC must offer a statutory review, to be accepted within 30 days, or the adviser can appeal to the tribunal (MTAR30600). Temporary relief pending the outcome must be granted where the suspension rests solely on an overdue amount or return; otherwise the adviser must show it could not continue as a going concern (MTAR30650).

Illustration only. A two director bookkeeping company files VAT returns for paying clients but has never held an agent services account or a Self Assessment agent code. It fell into the first window, which closed on 17 August 2026, so it should apply now. Because it has two officers, both directors are relevant individuals. One director’s own Self Assessment return for 2024 to 2025 is still unfiled, so the application will fail the overdue returns condition until that return is filed.

What are the most common mistakes?

Assuming a payroll bureau that also prepares accounts can wait for the payroll window.
Applying before AML supervision has been approved.
Overlooking a director’s or partner’s own late return or broken Time to Pay arrangement.
Forgetting the duty to tell clients about a suspension lasting more than 30 days.

Registration sits alongside professional body rules; see regulated vs unregulated accountants.

Solar Protect runs fee protection schemes for accountancy and bookkeeping practices. See how our accountant schemes work or read fee protection schemes for accountants.

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Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.