There is a new page on gov.uk, published on 24 August 2026, with a title that repays slow reading: "Check what to do if HMRC has signed you up for Making Tax Digital for Income Tax". Not whether to sign up. What to do now that it has happened to you.

From September 2026 onwards, HMRC will sign up taxpayers who were mandated into MTD for Income Tax from April 2026 and have not enrolled themselves, in stages over the coming months, based on qualifying income over £50,000 shown in their 2024-25 returns. The guidance describes no agent-facing notification: the confirmation letter goes to the client, into their HMRC online account or by post, and the department's own suggested first step for agents is to ask clients whether HMRC has been in touch. The income records seeding each sign-up are drawn from the 2024-25 return, and the guidance acknowledges the limits of that vintage: the records "may not include any changes to your circumstances since you last submitted a tax return".

So the reconciliation work lands, client by client, on the agent. This article sets out who gets swept up, what the checking procedure looks like in the Agent Services Account, which dates matter in September, and how to handle the records HMRC gets wrong.

The gov.uk page states the trigger plainly: "If you need to use Making Tax Digital for Income Tax for the 2026 to 2027 tax year and have not signed up yet, we will sign you up. This is because our records show your qualifying income was over £50,000 in the 2024 to 2025 tax year."

Two features of that sentence deserve attention. The determination runs off 2024-25 data, the most recent full return HMRC holds, so a client whose income has since fallen, or who ceased trading in 2025, can still be swept in. And the rollout happens "in stages over the coming months", with no published schedule of which taxpayers land in which stage. A client can be signed up in week one or week ten. The client gets a confirmation letter, which may sit unread in an online account; the agent hears nothing directly and finds out from the client or from the ASA.

Where a client should not be in the service at all, the guidance directs agents to the Agent Dedicated Line: "If you're an agent, you should contact the agent dedicated line if your client has been signed up and you disagree that they need to use the service." An exemption route also exists, for the digitally excluded among other grounds, with its own gov.uk application process. On the threshold itself, gov.uk answers the common boundary questions plainly: qualifying income counts the client's own share of jointly owned property income, gross before expenses, and excludes partnership profit shares.

The sentence doing the heaviest lifting in the guidance is the quietest one: the records "may not include any changes to your circumstances since you last submitted a tax return."

HMRC's pages, read together, describe a concrete workflow. Budget minutes per client, not seconds.

The guidance offers no bulk list or report; the route it describes is a per-client search of the Agent Services Account by UTR, confirming for each that the authorisation stands and MTD for Income Tax has been added. The practical move for a practice of any size is a triage list first: every SA client whose 2024-25 qualifying income (self-employment plus property, before expenses) exceeded £50,000 and who has not already enrolled, checked in priority order.

For each affected client, three mechanical checks: the agent authorisation is in place, the client's UTR shows in the ASA, and MTD for Income Tax is activated for them. Sign-ups completed by HMRC do not repair missing authorisations.

This is the substantive step. The service is seeded from the 2024-25 return, and the agent sign-up guidance is explicit about the job: "If your client has multiple self-employment income sources or property businesses, you'll need to check each one in the online service and add any that are missing." Ceased businesses may still appear. New 2025-26 or 2026-27 ventures will not. Business names, descriptions and addresses cannot be edited within the online service itself. The guidance splits the correction route by who is calling: Self Assessment: general enquiries for the taxpayer, the agent dedicated helpline for you. What matters on day one is that each live income source exists in the service and dead ones are ended correctly.

Auto-signed clients still need MTD-compatible software, and quarterly updates that fell due before the sign-up need catching up. The guidance orders the steps: access the online services, confirm the records, get software, catch up on digital records and quarterly updates.

Three dates shape the month.

The maintenance window sits awkwardly in the middle of the rollout's opening weeks, which is one more reason to run proactive enrolment on your own timetable rather than queuing sign-ups into an outage.

⚠️ Watch: the no-points easement covers quarterly updates in 2026-27 only, and the arithmetic underneath it is worth doing before anyone panics about the £200 charge. With quarterly points switched off that year, the single point available in respect of 2026-27 is the one for missing the 31 January 2028 return deadline, against a four-point threshold, and a point earned below that threshold clears itself 24 months later. Quarterly updates start earning points in 2027-28, which is when the threshold becomes genuinely reachable. The nearer risk is late payment: interest runs from day one, though a client in their first year gets 30 days from the due date to pay or agree a plan before penalties start, against 15 days afterwards.

Numbers make the workload honest, so take a practice with 300 Self Assessment clients and walk it through.

Suppose 70 of the 300 had 2024-25 qualifying income over £50,000 from self-employment or property. Perhaps 40 of those enrolled during the spring push, which leaves 30 candidates for automatic sign-up: sole traders who deferred, landlords mid-restructure, the two clients who never answer emails in summer. Those 30 are the triage list, and they can be identified from the practice's own 2024-25 return data in an afternoon, without touching the ASA once.

Assign realistic minutes: five to locate the client by UTR and confirm authorisation and activation, ten to reconcile income sources against what the practice knows, five to log the outcome and queue any fixes. Twenty minutes a client puts the 30-client sweep at ten working hours. That is a real cost, and it is the cheap version: the same 30 clients discovered piecemeal through the autumn, each surfacing via a confused phone call after an HMRC letter, cost multiples of that in interruptions alone.

The sensible order runs: build the list in the first week of September, and complete any proactive sign-ups before the maintenance window opens on the evening of Friday 11 September, because the stated outage covers the sign-up service itself. The quiet weekend suits drafting client communications; checks and source fixes carry on from the 15th. Clients with ceased businesses or missing new sources go to the front, because their records are the ones HMRC's 2024-25 seeding gets wrong, and wrong records generate wrong quarterly-update expectations from day one.

One proactive email to the 30, before HMRC's stages reach them, changes the entire dynamic: the practice announces the sign-up, explains the software position, and books the catch-up work on its own schedule. The alternative version of that conversation starts with a client forwarding an unexpected HMRC notification and asking why nobody warned them. Same work, opposite client experience.

Automatic sign-up is the enforcement arm of a timeline that keeps widening. On the current gov.uk guidance: qualifying income over £50,000 in 2024-25 meant MTD from 6 April 2026; over £30,000 in 2025-26 brings a client in from 6 April 2027; over £20,000 in 2026-27 brings them in from 6 April 2028.

Each tranche multiplies the same agent workload: triage, plumbing checks, source reconciliation, software, education. A practice that turns this September's scramble into a documented, repeatable procedure will run the April 2027 tranche, which reaches much deeper into the client base, at a fraction of the cost. The firms that treat it as a one-off will do the scramble three times.

The MTD questions clients actually ask sit at the boundary of guidance pages that change monthly: whether a jointly-let property counts toward qualifying income, how a mid-year cessation interacts with mandation, what an exemption application needs. Answering from memory is how stale guidance gets repeated. An AI tax research tool that reads the current primary guidance and cites it lets a practice answer at the speed clients expect during a rollout like this; we publish our accuracy benchmark so the reliability of those answers is a number rather than a hope, and our FAQ covers how the tool handles fast-moving guidance. For the fuller evaluation framework, see our guide to choosing AI tax research software.

Automatic sign-up changes the default. Until now, a mandated client who ignored MTD was a compliance risk on the client's side of the table; from September, they are a live service record on yours, seeded with year-old data, discovered only if you go looking. The guidance hands agents a genuine procedure, and it hands them the labour too: per-UTR searches, per-source reconciliation, catch-up submissions, all through a service that pauses for maintenance mid-month.

The practices that come through this well will be the ones that ran the list before HMRC did. If cited, current answers to MTD boundary questions would speed that work, create a GAIN Tax account, and find more rollout coverage on the GAIN Tax blog.

When does HMRC start signing clients up automatically? From September 2026, in stages over the coming months, for taxpayers mandated into MTD for Income Tax for 2026-27 (qualifying income over £50,000 in 2024-25) who have not signed up themselves. No stage-by-stage schedule has been published.

Will HMRC tell me which of my clients it has signed up? The guidance describes no agent-facing notification. The confirmation letter goes to the client, online or by post, and the suggested first step for agents is to check with clients whether HMRC has contacted them, then verify client by client in the Agent Services Account by UTR.

What data does HMRC use to set up the record? The 2024-25 return. The guidance acknowledges the records may not reflect changes since that return: ceased businesses can appear, newer income sources will be missing, and corrections to names or descriptions go through the agent dedicated helpline, or Self Assessment: general enquiries for the client, rather than the service itself.

What if my client should not be in MTD at all? Contact the Agent Dedicated Line to dispute the sign-up. A separate exemption application exists for the digitally excluded.

Are there penalties for missing quarterly updates this year? Per the current guidance, no penalty points arise for missed quarterly updates in the 2026-27 tax year. Check the penalties guidance before extending that comfort into 2027-28.

Who comes into MTD next? On the current timeline: qualifying income over £30,000 in 2025-26 brings taxpayers in from 6 April 2027, and over £20,000 in 2026-27 from 6 April 2028. Each tranche reaches deeper into a typical client base than the last, so the procedure a practice documents this September becomes the template for a much larger exercise in each of the following two springs.

Can a client's business names be corrected during sign-up? Not within the online service. The guidance gives two routes for changes to a business name, description or address: Self Assessment: general enquiries if the client calls, the agent dedicated helpline if you do. Inside the service an agent controls which income sources exist, adding missing ones and closing ceased ones so the quarterly-update expectations start from reality.