What Is Mandatory Agent Registration?

From May 2026, HMRC is introducing a new system of mandatory registration for accountants and tax advisers who interact with HMRC on behalf of clients.

Until now, most firms have operated using agent codes, Government Gateway access and Agent Services Accounts. Under the new rules, advisers will need to be formally registered with HMRC before they can act.

The purpose of this mandatory tax adviser registration with HMRC is to raise standards across the profession and give HMRC clearer oversight of who is representing taxpayers.

HMRC has confirmed that mandatory agent registration will begin from May 2026, with a transition period of at least three months.

That means firms will have a limited window to complete registration once the digital process opens, so preparation in advance will be essential.

Mandatory registration applies broadly to anyone who, in the course of business:

• assists clients with their tax affairs, and
• interacts with HMRC on their behalf

This includes most accountants in practice who file returns, deal with HMRC queries, or communicate with HMRC about client matters.

It is not limited to “tax specialists”. General accountancy firms providing VAT, payroll or other compliance services may also be in scope.

HMRC’s definition of interaction is wide. The new mandatory registration regime will cover activities such as:

• submitting returns
• writing to HMRC
• calling HMRC on behalf of clients
• using HMRC online services
• responding to compliance checks or enquiries

If your practice regularly acts as an intermediary between clients and HMRC, mandatory agent registration will almost certainly apply.

There are some limited exemptions within the mandatory tax adviser registration with HMRC rules.

These include, but are not limited to:

• most in-house tax teams dealing only with their employer’s affairs
• software providers with no advisory role
• certain customs-only intermediaries
• certain appeals-only work

However, most accountancy practices serving external clients should assume registration will apply unless clearly excluded.

Registration will not be automatic.

HMRC will apply eligibility conditions designed to ensure advisers meet minimum standards before they can act for clients.

These checks are expected to include:

Tax Compliance Requirements

A key condition is that firms and relevant individuals must be compliant in their own tax affairs.

• tax returns are up to date

• no outstanding liabilities

• any payment arrangements are being properly maintained

In short, advisers will need to meet the standards they expect clients to follow.

However, where returns or payments are outstanding, HMRC will use their discretion and consider the circumstances surrounding any failed compliance requirements.

2. Professional Conduct Standards

Mandatory registration will also link closely to HMRC’s Standard for Agents.

This sets expectations around:

• competence and reasonable care

• honest behaviour

• maintaining good records

• cooperating with HMRC

• protecting the integrity of the tax system

The new regime gives HMRC stronger powers to act where advisers fall below expected standards.

3. AML Supervision

Where applicable, mandatory tax adviser registration with HMRC will require firms to confirm they are properly supervised for anti-money laundering purposes.

Most accountancy practices are already supervised through a professional body or HMRC, but this will become a key eligibility requirement.

4. Fit and Proper Condition

The legislation provides ‘fit and proper’ conditions for senior decision‑makers (such as partners, directors and senior managers). Those individuals must not, for example, be disqualified as company directors, be subject to certain insolvency restrictions, or have relevant unspent convictions for serious tax offences.

This is not a one-off exercise.

Once registered, advisers will have continuing obligations, including:

• providing information HMRC requests

• notifying HMRC of relevant changes

• continuing to meet compliance and conduct standards

HMRC will also have powers to suspend or prohibit advisers from acting if requirements are not met.

For many firms, this will require operational planning, including:

• identifying who in the firm is in scope

• confirming senior staff meet eligibility conditions

• reviewing internal compliance processes

• ensuring continuity of service for clients

It also highlights the difference between simply having access to HMRC systems and being legally permitted to act under mandatory registration.

Although May 2026 may feel some way off, firms should begin preparing now by:

• reviewing their current agent setup

• checking internal tax compliance is up to date

• confirming AML supervision arrangements

• familiarising themselves with HMRC’s Standard for Agents

• planning who will lead the registration process within the practice

Early preparation will reduce the risk of disruption when the mandatory agent registration service opens.

Mandatory agent registration represents one of the most significant operational changes for accountants in practice in recent years. Understanding the requirements now will help firms stay compliant, protect client relationships, and avoid last-minute issues as implementation approaches.

Practice Forum Discussions

Want to know how other firms are preparing for mandatory agent registration? Join our March and April Practice Forum sessions to compare approaches, share challenges, and gain practical insight from firms already planning ahead. 

Training and guidance

Stay ahead of the new mandatory agent registration rules. Our specialist webinars break down the process, timelines, and eligibility requirements, giving your practice the clarity and confidence it needs. Secure your place now.

Book Webinar Part 1 – Getting Started Before May 2026

Book Webinar Part 2 – Preparing to Register