MTD sign up issues: practical guidance for agents

As the end of the first quarterly update period for Making Tax Digital (MTD) for Income Tax approaches, many agents will be registering clients for the service. In most cases, the process is straightforward and completed without difficulty. However, where problems do arise, they can often be resolved quickly by checking a few common issues before contacting HMRC.

One of the most frequent problems agents encounter is difficulty logging into the Agent Services Account (ASA). This is usually caused by the agent using the wrong Government Gateway credentials. The ASA has its own user ID and password, which are separate from those used for the older agent online services account, which has been used for self-assessment to date. Using incorrect credentials can also prevent you from authorising MTD compatible software. If you are confident that the login details are correct, but the issue persists, it can be helpful to report the issue using HMRC’s online ‘Report a Problem with this Page’ button. ATT has more information on reporting problems in this article. Providing as much detail as possible will ensure the issue is directed to the appropriate team. In many cases, waiting 72 hours after reporting and trying again resolves the problem. If not, contacting the MTD helpline is the next step.

Another issue that can arise is HMRC being unable to find a client when you are attempting to register them for MTD. In the first instance, you should check that all client authorisations have been copied across to your ASA. HMRC provides guidance on how to do this here: Add your client authorisations for Making Tax Digital for Income Tax - GOV.UK It is also important to ensure that all agent online services accounts you use for self-assessment are correctly linked to your ASA.

More information on the ASA and authorisations can be found here.

If the client authorisation still cannot be located by HMRC during the registration process, it is worth confirming that a valid authorisation is in place by searching for them in your agent online accounts. If no 64-8 is in place, then agents will need to be authorised either by submitting a 64-8 or using an ASA MTD digital handshake. A 64‑8 provides broader authorisation across HMRC services, while the digital handshake applies specifically to MTD.

Sometimes the issue lies not with authorisation but with the client’s tax return history. For example, if the client’s 2024/25 tax return has not yet been processed by HMRC, they may not yet have been identified as having MTD qualifying income and therefore potentially eligible for MTD. This is more likely where returns have been submitted on paper or require manual processing. A call to HMRC may be able to expedite the processing.

It is also worth checking that the National Insurance number (NINO) you hold is correct, as the ASA uses this to identify clients. Although uncommon, discrepancies in HMRC’s records can occur and may require HMRC to investigate and correct the data. This will require a call to HMRC to ask them to do a sweep of their system to identify the erroneous NINO.

Agents may also encounter error messages stating that a client is not eligible for MTD. In many cases, this is because the client falls within one of the automatic exemption or 2026/27 deferral categories. Reviewing the client’s most recent tax return will usually clarify whether an exemption or deferral applies. Further detail on exemptions is available in the ATT’s guidance: Making Tax Digital: exemption cases, when and how to apply. It is also possible that a digital exclusion exemption has been requested for the client, which would prevent sign‑up.

In less common cases, the issue may be caused by outdated flags on HMRC’s system, such as those linked to historic enquiries or payment issues. These should no longer prevent a client from using MTD, so where this appears to be the cause, contacting HMRC to have the restriction removed is recommended.

If, after carrying out these checks, the issue remains unresolved, there are several routes for further support. HMRC’s Agent Dedicated Line should be used for registration problems, choosing options 2 then 3, while technical issues with software should be referred to the relevant provider. Where the difficulty appears to relate to an HMRC webpage or system error, reporting it online using the ‘report a problem with this page’ function can help ensure that it is investigated.

The ATT also provides support to members experiencing persistent problems. Agents can get in touch by email at [email protected] or raise an issue using the ATT’s online form Report a New Issue With HMRC Systems To The ATT . 

By working through these common causes methodically, most MTD sign‑up issues can be resolved without significant delay. Although issues are uncommon, it is advisable to complete client registrations well ahead of the first quarter submission deadline to ensure any potential problems can be addressed without causing delay.