To sign a client up for Making Tax Digital for Income Tax, an agent needs an agent services account, a valid authorisation from the client, and then a separate sign up for each client through HMRC’s online sign up service. Adding existing Self Assessment authorisations to the agent services account makes the firm the main agent, but it does not sign anyone up; that step is always done client by client.

Which clients need to be signed up, and from when?

HMRC’s sign up guidance for agents says a client must use Making Tax Digital for Income Tax from 6 April 2026 if their qualifying income is over £50,000. Qualifying income is the total of self employment and property income before expenses (turnover), taken from the tax return for the previous tax year. The roll out is staged by reference to earlier returns:

Return used to test income Qualifying income Start date
2024 to 2025 more than £50,000 6 April 2026
2025 to 2026 more than £30,000 6 April 2027
2026 to 2027 more than £20,000 6 April 2028

To be signed up, the client must be registered for Self Assessment and have submitted a tax return in the last 2 years. The return for the tax year before the client starts is still filed through ordinary Self Assessment. Clients who may be exempt, for example because they are digitally excluded, should be checked before sign up rather than after. The obligations themselves sit in the Income Tax (Digital Obligations) Regulations 2026 (SI 2026/336), made under Schedule A1 to the Taxes Management Act 1970. For who is in scope and why, see our overview of Making Tax Digital for Income Tax.

What does the firm need in place before signing anyone up?

The firm needs an agent services account. HMRC is explicit that this is different from the HMRC online services for agents account used for traditional Self Assessment. The sign up service has to be used with the same user ID and password as the agent services account, so staff who only hold the older online services credentials cannot complete it. Our page on the HMRC agent services account covers applying for one and setting up staff access.

HMRC’s agent step by step guide also expects the firm to have chosen software before sign up, and the choose agents guidance asks agents to check that the client has approved the chosen software. Agreeing the software in the engagement terms avoids a dispute later about who pays for licences.

How does the agent get the client’s authorisation?

There are two routes, depending on whether the firm already acts for the client in Self Assessment.

Clients already authorised for Self Assessment

HMRC recognises existing Self Assessment authorisations for Making Tax Digital for Income Tax, but they must be visible in the agent services account. The firm signs in and selects “Add existing Self Assessment authorisations to your agent services account”. This screen lists the Self Assessment agent codes already added; it does not list individual clients. If a code is missing, the firm adds it, and every client authorisation linked to that code is brought across. Firms with more than one agent code repeat the process for each code.

According to HMRC’s guidance on adding authorisations, this step:

  • keeps access in the HMRC online services account, which is still used for Self Assessment clients outside the new rules;
  • makes the firm the main agent for those clients;
  • links the two accounts, so adding or updating Self Assessment clients in online services updates permissions in the agent services account; and
  • does not sign any client up.

If the firm stops acting for a client, it must delete the authorisation in both accounts.

New clients, or a supporting agent role

Where there is no existing Self Assessment authorisation, the firm uses the digital handshake. In the agent services account the firm selects “Ask a client to authorise you”, enters the client’s details and receives an authorisation request link to send to the client. The link expires after 21 days, after which the request has to be started again. Progress can be checked on the “Manage your authorisation requests from the last 30 days” page. The client sees a different consent statement depending on whether the firm has asked to be a main or a supporting agent; the differences are set out in main and supporting agents under MTD.

What information does the sign up service ask for?

HMRC lists the details needed to sign up a client:

  • full name, date of birth and National Insurance number;
  • for a sole trader, the business name used on invoices, the business address and the nature of the trade;
  • for each income source, the start date if the business or property income began within the last 2 tax years;
  • confirmation of the tax year in which the client will start.

Where a client has several trades or property businesses, each one must be checked in the service and any missing source added. Sources that have ceased since the last return should be reported too. If every self employment and property source has ceased, HMRC must be told before the start of the next tax year, otherwise the client will still need to use the service. Other income such as dividends or savings is not asked for at sign up; it is added later in the software before the tax return is submitted.

What happens straight after sign up?

The firm connects its software to HMRC using the agent services account credentials, passes an identity check using personal information of someone at the firm, and grants permission. HMRC says this must be repeated every 18 months. The accounting period then needs checking. Software defaults to periods matching the tax year; a client whose accounting period runs from 1 April to 31 March should be set to calendar update periods before the first quarterly update, because the choice cannot be changed once an update has been sent.

For a client starting on 6 April 2026, HMRC’s first year timetable gives quarterly update deadlines of 7 August 2026, 7 November 2026, 7 February 2027 and 7 May 2027, with the tax return due by 31 January 2028. A client signed up part way through the year must catch up, creating digital records from the start of the tax year. HMRC will not apply penalty points for late quarterly updates in 2026 to 2027, although late returns and late payment still attract penalties.

What if HMRC has already signed the client up?

From September 2026 HMRC began signing up people who need to use the service for 2026 to 2027 but had not signed up, where its records show qualifying income over £50,000 for 2024 to 2025. HMRC uses only the information it already holds, so recent changes in circumstances may be missing. HMRC tells agents to check that the authorisation has been added, that the client’s Unique Taxpayer Reference appears in the agent services account and that the new service has been added, and then to review the income sources HMRC holds for each client. If the firm disagrees that a client should be in the service, HMRC directs agents to the agent dedicated line.

Can a client volunteer early?

Yes. A client can sign up for the current tax year or the next one before they are required to. Any quarterly updates already missed for the year so far must be sent through compatible software. Volunteers are subject to a different set of penalty rules, and HMRC says it will contact the client to confirm when those penalties start to apply. Volunteering suits clients with simple affairs who want a practice year, but it is a poor choice for a client whose records are not yet in usable shape.

How might this work across a client list?

Illustration only. A practice has three clients. Client A is a landlord whose 2024 to 2025 return showed £62,000 of rent, already authorised under the firm’s Self Assessment agent code. Client B is a sole trader with £41,000 turnover who has just joined the firm. Client C, a hairdresser with £55,000 turnover, also has a separate bookkeeper.

  • Client A: the firm confirms its agent code appears in the agent services account, then signs A up for 2026 to 2027 using A’s National Insurance number and property details.
  • Client B: B is not required to start until 6 April 2027, based on the 2025 to 2026 return. The firm sends a digital handshake link as main agent now and diarises sign up well before that date.
  • Client C: the firm is main agent and the bookkeeper asks C to authorise them as a supporting agent. Either agent can sign C up, but both should agree who does it so the start year and income sources are entered once and correctly.

What mistakes come up most often?

  • Assuming that adding agent codes has signed clients up. It has not.
  • Trying to use HMRC online services credentials in the sign up service.
  • Leaving calendar update periods unset for a 31 March year end until after the first update.
  • Not reporting ceased businesses, so HMRC keeps expecting updates for them.
  • Letting digital handshake links expire after 21 days without chasing.
  • Forgetting the 18 month software reauthorisation, which stops submissions at a busy deadline.

Key dates for the wider year are in our UK tax deadlines calendar.

Solar Protect runs fee protection schemes for accountancy and bookkeeping practices. See how our accountant schemes work or read fee protection schemes for accountants.

Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.