HMRC tax adviser registration: the 18 November 2026 deadline accountants should check now

A new HMRC registration requirement is moving through the UK tax-advice market in stages, and the current window matters particularly to smaller accounting and bookkeeping practices. From 18 August 2026, advisers who already have a Self Assessment or Corporation Tax agent account but do not have an Agent Services Account have been required to register under HMRC’s new mandatory tax adviser registration rules. Their three-month window closes on 18 November 2026.

This is not limited to firms that describe themselves as tax advisers. HMRC says a business can be in scope if it is paid to interact with HMRC about another person’s tax affairs, including by submitting returns or claims, making payments, or communicating with HMRC on a client’s behalf. The practical test is what the business does, not the label on its website.

Who is in the 18 November 2026 registration window?

The second phase applies to advisers that already have a Self Assessment or Corporation Tax account but do not yet have an Agent Services Account. HMRC opened this phase on 18 August 2026 and says eligible advisers have until 18 November 2026 to apply.

What HMRC means by a tax adviser

HMRC’s guidance says the legal entity that interacts with HMRC must register. Individual employees do not register separately, but HMRC will carry out checks on certain people within the business. A sole trader can therefore be the registering legal entity, while a company or partnership registers as the business that provides the paid service.

There are important exclusions. HMRC says registration is not required where a person only deals with HMRC as part of an in-house tax team, only deals with their own company group’s affairs, gives tax help for free, or only develops or provides accounting, tax or payroll software. There are also specific exemptions for some activities such as customs, certain representative roles and tribunal work. Practices with mixed services should use HMRC’s checker rather than relying on one exempt activity to decide the position for the whole business.

What conditions must a practice meet?

Registration is more than creating a login. HMRC says the business must meet registration conditions. The practice must provide evidence that it is supervised for anti-money laundering purposes, for example a supervision certificate or confirmation email. HMRC also checks matters including relevant outstanding tax returns or unpaid tax, formal insolvency, relevant unspent convictions for fraud or tax offences, and whether the business is subject to certain sanctions or restrictions.

HMRC also identifies relevant individuals inside the business. For a practice with five officers or fewer, all officers are treated as relevant individuals. For a business with six or more officers, the focus is on people who make strategic or management decisions about the tax-advice activity, with HMRC requiring at least five relevant individuals in some cases. Those individuals are checked against similar conditions and must not be disqualified from acting as a director.

A five-step checklist before you apply

1. Confirm which legal entity provides the paid tax service and check whether it already has an Agent Services Account. Do this at firm level rather than assuming each employee needs a separate registration.
2. Use HMRC’s registration checker to confirm which window applies. This is especially important for firms that combine bookkeeping, payroll, tax returns, VAT and advisory work because the payroll-only later window applies only where the business does not interact with HMRC in any other way.
3. Gather the business credentials for the application, including the business Government Gateway details and the firm’s Unique Taxpayer Reference. Sole traders may also need their personal Government Gateway details.
4. Check the registration conditions before submitting. Make sure anti-money laundering supervision evidence is available, identify the relevant individuals HMRC may need to check, and resolve any relevant outstanding filing or payment issues where possible.
5. Submit before the deadline and keep an internal record of the application. HMRC says advisers can continue interacting with HMRC during their three-month registration window and while an application is being considered, so applying early gives more time to respond if HMRC requests further information.

What happens if you do not register?

HMRC says a business that is required to register but does not do so may lose the ability to interact with HMRC on behalf of clients. Its August announcement also says continued operation without completing the requirement can lead to enforcement action, including financial penalties. HMRC says it will give businesses an opportunity to correct issues or respond before a sanction takes effect.

For a small practice, the operational risk may be as important as the formal sanction. If an adviser cannot use HMRC services for a client at the point a return, claim or payment needs action, the disruption can affect deadlines and client trust. Treat registration as a practice-management task rather than something to leave until the final week.

What accounting practices should do this week

If your firm has Self Assessment or Corporation Tax agent access but no Agent Services Account, put the 18 November 2026 deadline into the compliance calendar now and assign one person to verify the firm’s position. Check the exact legal entity, registration window, anti-money laundering supervision and relevant individuals, then start the application while there is still time to resolve questions.

If you already have an Agent Services Account, there is no need to submit a duplicate application. Instead, keep the account details current and watch for HMRC messages requesting further information. If you are outside the current phase, record the later date that applies to your business rather than assuming the requirement does not affect you at all.