Mandatory registration of tax advisers: what you need to know

Author: Jen Badger Published: 30^th September, 2026

This year HMRC introduced mandatory registration for tax advisors. As we reach the half-way point of the staged registration timetable, here’s our summary of how this affects R&D tax advisors and everything you need to know to stay on the right side of the new requirements.

Why did HMRC introduce registration?

HMRC’s stated goal for mandatory registration is ensuring that all tax advisers interacting with HMRC on behalf of their clients meet minimum requirements. Registration will enable them to more closely monitor tax advisers and exclude those that do not or cannot meet the standards. From an R&D tax relief perspective, this measure should reduce the number of ‘rogue’ advisers in the marketplace and continue the trend we’ve seen of reduced error and fraud and improved standards within the sector.

Who has to register?

Anyone who interacts with HMRC about someone else’s tax affairs, and gets paid for this, is considered by HMRC to be a tax adviser and is therefore required to register.

In this context, interacting with HMRC includes:

Phone, post or email,
Messages through the HMRC website or app
Making payments
Sending returns, claims or other documents

Given these rules and definitions, you can see that the requirement to register is fairly broad and wide ranging, and would apply to any R&D tax relief adviser who interacts with HMRC at any point during the process.

There are some exemptions to the need to register, for example in-house tax teams, but these would not apply to advisers working in R&D tax relief advice.

When and how can I register?

Advisers are required to register through the standard agent service account service. The need to register has been rolled out gradually with different groups invited to register in each wave. As of September 2026, all advisers should have registered for an agent services account, except:

Those with a Self Assessment or Corporation Tax agent account should register from 18^th August 2026
Those who only provide third-party payroll services for clients and do not otherwise interact with HMRC must register from 18 November 2026 onwards
Financial services organisations must register from 31^st December 2026 onwards.

Most R&D tax relief advisers will have been required to register in the wave that started on the 18^th May 2026 and ended on the 18^th August 2026.

What happens if I don’t register?

All advisers have three months from their start date to apply for their agent services account. Advisers who don’t register will no longer be able to interact with HMRC on behalf of their clients.

Want to know more?

If you have any questions about this, or would like to know more about how the WhisperClaims software and our team can help you stay compliant and make confident decisions under the new regime, get in touch!

Let’s talk