HMRC's tax adviser register: the 17 November deadline

November 13, 2026

London · November 2026

Tax advisers who already have a Self Assessment or Corporation Tax account, but do not have an agent services account and do not fall into a later registration phase, have until the end of Tuesday 17 November 2026 to apply to register with HMRC. HMRC's mandatory tax adviser registration manual sets the window for this group as 18 August to 17 November 2026. Accountancy Daily reported on the deadline on 12 November.

HMRC's public guidance, last updated on 3 September 2026, says that if you are paid to interact with HMRC about someone else's tax affairs, HMRC treats you as a tax adviser and you need an agent services account, unless an exemption applies. That includes phone, post or email, messages through GOV.UK or the HMRC app, making payments, and sending returns, claims or other documents. It applies even if you do not describe the work as tax advice, and even if you act for only one client. The legal entity must register, not individual employees, though HMRC will carry out checks on certain people in the business. A firm that already has an agent services account does not need to register again.

The requirement is being introduced in stages. The payroll window runs from 18 November 2026 to 17 February 2027. It applies to advisers without an agent services account whose only tax adviser activity is providing third-party payroll services and who do not qualify for the financial services phase. For financial services organisations without an agent services account that qualify for the later phase, the application window runs from 31 December 2026 to 31 March 2027. You can continue to interact with HMRC on behalf of clients during your application window. If you apply within that window, you can continue while HMRC considers your application. You can also apply early. If you missed your window or are new to the market, HMRC says you should apply now.

What happens if you do not register

If you need to register and do not, HMRC's guidance says you may not be able to interact with HMRC on a client's behalf, and may face sanctions if you continue to try while unregistered. HMRC says it will give you a chance to correct any issues first. A separate HMRC page on unregistered or suspended advisers sets out the sanctions in more detail. The first prohibited interaction leads to a formal compliance notice, requiring you to stop interacting with HMRC on behalf of clients until you are registered. Each prohibited interaction after that notice can attract a £5,000 penalty. If you receive five penalties within a two-year period, starting on the date of the first penalty, the fifth penalty is £10,000 and you face a 12-month ban. Any further prohibited interaction in the same two-year period attracts a £10,000 penalty. A prohibited interaction during that ban leads to a permanent ban and a £10,000 penalty. Each prohibited interaction during a permanent ban can attract a further £10,000 penalty.

The working files behind a submission

HMRC's performance update for July to September 2026, published on 12 November, reports on both compliance work and the register. More than 2,900 new compliance staff have joined since Autumn Budget 2024, including over 470 between July and September. HMRC says greater use of artificial intelligence will help it identify potential non-compliance more quickly, and that new powers to tackle dishonest tax advisers will help close the tax gap. The same update records that more than 4,400 applications were processed in the first registration phase, with the second phase now under way.

The registration rules govern who may deal with HMRC on a taxpayer's behalf, and HMRC is putting more resource into spotting non-compliance. The pay runs, Real Time Information (RTI) files and working papers behind each submission usually still sit in the adviser's or payroll bureau's own systems. When a file is questioned years later, or handed over after a firm fails, it can be hard to show that the copy produced has not been changed.

A dated receipt for the file

A dated receipt for the working file, recorded when the file is used or handed over, does a narrow job. It does not show that a figure is right, who prepared the file, or when the document was first created. It can record a file's fingerprint. To check a copy later, compare its fingerprint with the one on the receipt.

I handle business development and communications for Partisan. Partisan records a file's fingerprint without seeing or keeping the file, and issues a dated receipt. You can use the receipt to check whether another copy has the same fingerprint. A short account of what it does is here: What Partisan does.

Charles Pycraft

This note is general commentary on public sources and is not tax advice.