Following a recent meeting with HMRC, there are a number of important developments to be aware of regarding the introduction of Mandatory Tax Adviser Registration (MMTAR).
With the regime now enacted and registration open from 18 May 2026, the direction of travel is becoming clearer. HMRC is placing particular emphasis on how firms interact with them in practice, rather than how services are structured on paper.
Of particular note are concerns around outsourcing arrangements, where there appears to be a growing risk of firms misunderstanding whether they fall within scope. The message from HMRC is increasingly consistent: if your business is involved in tax work and engages with HMRC on behalf of clients in any form, you should be carefully assessing your position now.
Set out below is a summary of the key points arising from that discussion, along with areas where further clarification is expected.
Overview of MMTAR
- The Finance Bill provisions have now been enacted, with registration opening on 18 May 2026.
- The regime applies at the business (legal entity) level, not to individual staff.
- It captures businesses that:
- Provide tax services to clients for payment; and
- Interact with HMRC on their behalf (including submission of SDLT returns, repayment claims, and importantly, the payment of SDLT).
- Firms with an existing Agent Services Account (ASA) will be automatically migrated, with additional information to follow.
Outsourcing – Key Area of Concern
- HMRC explicitly raised concerns regarding mixed and conflicting messaging from outsourcing providers.
- There is a clear risk that firms may enter into outsourcing arrangements under the misapprehension that this removes the requirement to register.
- HMRC reiterated that:
- The key test is interaction with HMRC, not the contractual structure.
- Paying SDLT is treated as interaction, and therefore brings an entity within scope.
- Stakeholders strongly emphasised the need for urgent, clear and consistent guidance, and HMRC acknowledged this as a priority area requiring clarification.
Relevant Individuals
- Firms must identify “relevant individuals” responsible for governance, oversight, or decision-making.
- HMRC has clarified that:
- This does not include junior staff or those simply carrying out work.
- Smaller firms may need to include all partners/members.
- Larger firms should identify a limited but appropriate group.
- Further guidance and case studies are expected, with HMRC indicating a pragmatic and engagement-led approach to any initial inaccuracies.
Terminology
- HMRC confirmed that they will not engage in discussions regarding the use or interpretation of the term “tax adviser” for the purposes of MMTAR.
- Firms should therefore proceed on the basis of the legislative definition and scope, rather than expecting flexibility in terminology.
Operational and Transitional Points
- During the initial implementation period:
- SDLT returns will not be blocked where a registration number is not yet included.
- Any future enforcement changes will be clearly communicated in advance.
- Third-party software/API submissions are considered interaction with HMRC.
Next Steps and Further Guidance
- HMRC confirmed:
- There will be no public register of tax advisers.
- Ongoing engagement with professional bodies and stakeholders will continue.
- Further clarification is expected on:
- Outsourcing scenarios (particularly urgent)
- Identification of relevant individuals
- Registration timing and transitional arrangements
Given the emphasis placed by HMRC on outsourcing and interaction (including SDLT payments), firms should review their current operating models and get in touch if you have any questions.
I will continue to monitor developments and provide further updates as additional guidance is released.
Getting in touch
If you would like to discuss a particular matter, please feel free to contact me at amanda@bhptax.law in the first instance. Our SDLT team can also be reached at freya@bhptax.law.
If you would like to arrange a training session for your team on SDLT or property tax risk areas, Olivia would be very happy to assist and can be contacted at olivia@bhptax.law.
