The agent services account is HMRC’s online account for tax advisers, and since 18 May 2026 applying for one is also how a paid adviser registers with HMRC under the mandatory tax adviser registration rules in the Finance Act 2026. Clients then authorise the firm through the account (the “digital handshake”), through Online Agent Authorisation or on form 64-8, depending on the tax.
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What is an agent services account and who needs one?
HMRC describes the agent services account (ASA) as the way tax advisers access HMRC’s online services for clients. It is needed for services such as VAT, Making Tax Digital for Income Tax, Capital Gains Tax on UK property accounts and Pillar 2 top up taxes, and HMRC has required it since May 2023 for anyone claiming Income Tax or PAYE repayments on behalf of others. Self Assessment, Corporation Tax and PAYE still also run through the older HMRC online services for agents account, so most practices hold both.
From 2026 the ASA is more than an access tool. HMRC’s guidance says that if you interact with HMRC about someone else’s tax affairs and get paid for it, you must register with HMRC as a tax adviser, and registration is done by applying for an ASA. That applies even if the firm only deals with HMRC by post or phone.
What changed with mandatory tax adviser registration?
HMRC’s Mandatory Tax Adviser Registration manual (MTAR10100) explains that the registering person is the legal entity providing the service, and that a tax adviser is defined in section 224 of the Finance Act 2026 as an organisation or individual which, in the course of a business, assists clients with their tax affairs. Employees and partners do not register personally, but HMRC checks “relevant individuals” in the business. Assistance includes helping to prepare any document HMRC is likely to rely on, so a bookkeeper who deals with HMRC for paying clients can be in scope even without seeing itself as a tax adviser.
Registration is being phased in. MTAR10800 gives the windows:
| Registration window | Who |
|---|---|
| 18 May to 17 August 2026 | New advisers, or those dealing with HMRC without an ASA, Self Assessment or Corporation Tax agent account |
| 18 August to 17 November 2026 | Advisers with a Self Assessment or Corporation Tax agent account but no ASA |
| 18 November 2026 to 17 February 2027 | Payroll only advisers without an ASA |
| 31 December 2026 to 31 March 2027 | Financial services organisations without an ASA |
Firms that already had an ASA before 18 May 2026 do not reapply, but MTAR30700 says they became subject to the ongoing registration conditions and the sanctions framework from 18 August 2026. A firm offering accountancy as well as payroll falls into the earlier tranche, not the payroll one.
Sanctions include suspension, compliance notices and ineligibility orders. MTAR30400 explains that an adviser who keeps interacting with HMRC for clients while under a compliance notice faces a penalty of £5,000 for each prohibited interaction under sections 234 and 235 of the Finance Act 2026, rising to £10,000 after four or more such penalties in two years or where an ineligibility order is in force. Reasonable excuse is a defence and HMRC must allow 30 days for representations first.
Illustration only. A sole practitioner bookkeeper files Self Assessment returns using an agent code but has never set up an ASA. She falls in the second window, so she can keep acting for clients while she applies before 17 November 2026, and while HMRC considers the application.
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What do you need to apply?
HMRC’s create an agent services account guidance lists a business Government Gateway user ID, the firm’s Unique Taxpayer Reference and its postcode, the company registration and VAT numbers if the firm has them, the name of its anti money laundering supervisor with proof of supervision, and details of relevant people in the business. Since 1 October 2026 the guidance warns that HMRC will reject an application if AML supervision has been applied for but not yet approved. See AML supervision for accountants.
HMRC’s conditions guidance adds that the business must not have outstanding returns or unpaid tax outside a payment plan, relevant unspent convictions for fraud or tax offences, or be formally insolvent. Where a firm has five or fewer officers, all of them are treated as relevant individuals. HMRC’s published processing time for an ASA is 40 working days. Applications are measured against the HMRC Standard for Agents.
How does a client authorise an agent?
HMRC’s authorisation guidance gives different routes depending on the tax:
| Tax | Online route | Paper route |
|---|---|---|
| VAT, Capital Gains Tax on UK property, Trust Registration Service | Digital handshake in the ASA | None listed |
| Making Tax Digital for Income Tax | Digital handshake, or copying Self Assessment authorisations into the ASA | None listed |
| Self Assessment, Corporation Tax | Online Agent Authorisation | Form 64-8 |
| PAYE | Online Agent Authorisation or the client’s business tax account | Form 64-8 |
For the digital handshake, the agent selects “Ask a client to authorise you”, enters the client’s details and receives a link to send. HMRC says the link expires after 21 days, after which the process starts again. For Online Agent Authorisation, HMRC posts a code to the client within 7 working days, the client must pass it to the agent within 30 days of the letter, and three wrong attempts at entering it mean starting again. HMRC withdrew Online Agent Authorisation for VAT from 16 February 2024.
How does authorisation work for Making Tax Digital for Income Tax?
HMRC’s guidance on choosing agents introduces two levels. A main agent can do almost everything the client can, except set up a Direct Debit or change how HMRC contacts the client. A supporting agent sees only business and property income and cannot submit the return, view the tax calculation or finalise the overall position. A client can have one main agent at a time and any number of supporting agents, which suits a bookkeeper doing quarterly updates alongside an accountant doing the final declaration.
Firms with an ASA can add existing Self Assessment authorisations by selecting “Add existing Self Assessment authorisations to your agent services account” and working through each agent code. Every client linked to that code is added and the firm becomes their main agent, but clients are not signed up to MTD automatically. Our page on Making Tax Digital for Income Tax covers who must join.
How should staff access be set up?
HMRC says each member of staff should have their own Government Gateway user ID, with permissions set to control which services and clients they can see. Shared logins make it impossible to show who submitted what, and leave access open when someone leaves. Removing leavers promptly is also a data protection point; see data protection for accountancy practices.
What happens when the practice changes structure or closes?
HMRC’s guidance on changing agent businesses says that a new legal entity, for example a sole practitioner incorporating, needs a new ASA under the new UTR and fresh client authorisations. It states that you must not try to move agent codes from the old legal entity to the new ASA, and that doing so breaches the HMRC Standard for Agents and UK GDPR. On closure, the firm must remove all clients from both accounts and write to the Agent Compliance Team with the cessation date, agent codes and Agent Reference Number. The wider steps are in selling or closing an accountancy practice.
What are the common mistakes?
- Assuming a Self Assessment agent code counts as registration. It does not; such firms fall in the second window.
- Applying for an ASA before AML supervision is approved.
- Letting a digital handshake link expire after 21 days without chasing the client.
- Treating a supporting agent authorisation as enough to file the final MTD return.
- Copying agent codes into a new company’s ASA after incorporation.
Solar Protect runs fee protection schemes for accountancy and bookkeeping practices. See how our accountant schemes work or read fee protection schemes for accountants.
Related Accountapedia entries
- Mandatory registration of tax advisers with HMRC
- HMRC agent reference numbers and codes
- Copying authorisations into the agent services account
- Form 64 8: when it is still used
- Authorising an agent for trusts and estates
Sources
- GOV.UK: Get an hmrc agent services account
- GOV.UK: Find out how to register as a professional tax agent with hmrc
- GOV.UK: Manual page MTAR10100
- GOV.UK: Manual page MTAR10800
- GOV.UK: Manual page MTAR30700
- GOV.UK: Manual page MTAR30400
- GOV.UK: Check if you meet hmrcs conditions to register as a tax adviser
- GOV.UK: How to get authorised to act as a tax agent on behalf of your clients
- GOV.UK: How to use the digital handshake to get authorised as a tax agent
- GOV.UK: How to use the online agent authorisation to get authorised as a tax a
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.