On 18 August 2026 a piece of administrative housekeeping became a sanctions regime. The Finance Act 2026 requirement for tax advisers to register with HMRC has been on the statute book since Royal Assent in March; what changed in August is that the first commencement tranche went live, and with it the machinery of penalties, ineligibility orders and, most strikingly, a power for HMRC to publish the names of sanctioned advisers.

The profession's attention has been elsewhere, on Budget speculation and the autumn filing season. Meanwhile a regime that can price a single phone call at £5,000 became law in force with little ceremony. Nothing here was hidden, every provision sits in public on legislation.gov.uk, and the details reward a careful read.

This article sets out who must register, what a prohibited interaction is, how the sanctions escalate, and the checks worth running in any practice this month. Every claim below is drawn from the Finance Act 2026 itself and the commencement regulations, with HMRC's new manual as corroboration.

Section 224 defines a tax adviser widely: an organisation, or an individual trading alone, that assists other persons with their tax affairs in the course of a business. Assistance covers advising, acting as agent, and helping with documents HMRC will rely on. An appointment routed through another firm still counts.

Two boundaries matter as much as the definition.

An individual who works for a tax adviser and interacts with HMRC in the course of that business is not personally required to register; the interaction is attributed to the employer firm. Registration is a firm-level duty for employed staff, a personal one for sole practitioners.

The shield is narrower than it looks, though. Under section 235, a "relevant individual", the officers, partners and senior people who play a significant role in managing or organising the firm's tax-adviser activities (s. 226), faces the same £5,000 and £10,000 penalties personally where the firm's contravention is attributable to them, and section 237 allows personal ineligibility orders against them. The same interaction is never penalised on both: sections 234(1)(c) and 235(1)(c) are mutually exclusive, turning on whether an officer considers the contravention attributable to a relevant individual. Liability lands on the firm or on the person, never on each for the same interaction. Section 243 does separate work, barring a penalty where the same conduct has produced a criminal conviction. Junior staff are protected; the tax-team head is not.

The business requirement excludes the neighbour who helps with a Self Assessment return for nothing. Do it in the course of a business, of which charging is the strongest signal rather than the test itself, and the definition bites; the one-off paid favour is a genuine boundary case, examined below.

⚠️ Watch: the prohibition is extraterritorial. Section 223 applies "even if the tax adviser or the client (or both) are outside the United Kingdom". An overseas firm handling UK filings for UK clients is inside the regime, wherever its office sits.

Section 223 prohibits an unregistered tax adviser from interacting with HMRC in relation to the tax affairs of a client. The definition of interaction is deliberately broad: a phone call, a letter, an email, a message through a website or portal, filing a return, claim, notice or other document, or communicating in any other way. Section 223(2) covers attempts as well as completed acts, so a call that fails to connect and a filing HMRC rejects both count.

The penalty mechanics have a trigger worth understanding, and it comes with two exits rather than one. Before serving a compliance notice, HMRC must notify the adviser and allow 30 days for representations (s. 233(7)). Once the notice lands, interactions before it draw no section 234 penalty and every interaction after it draws its own charge. The second exit matters more: the notice is treated as withdrawn if the adviser then registers, or if a suspended registration is lifted or expires (s. 233(4) to (6)). Registering closes the exposure; ignoring the notice is what keeps the meter running.

Schedule 20 carves out specific interactions: software providers supplying payroll, tax or accounting software, acting in that capacity; customs, excise and import VAT matters; VAT representatives; IOSS representatives; NI tax representatives; UK representatives; interactions about taxes that are not payable to HMRC, such as council tax and non-domestic rates; Valuation Office property valuations under section 10 CRCA 2005; interactions concerning clients that are related group undertakings, the in-house carve-out; appeals before a court or tribunal; interactions required to comply with a statutory obligation; and responses to an HMRC information request.

Three of those exceptions arrived by SI 2026/815, in force on 17 August 2026, the day before the sanctions themselves. A list copied from the Act as enacted is therefore already wrong, which is a fair warning about this whole regime: read the amended schedule, not the printed one, and assuming an exception without checking it is how firms end up testing the penalty provisions.

The standard penalty is £5,000 for each prohibited interaction after an unwithdrawn compliance notice. The enhanced £10,000 rate applies in two situations: the adviser has been assessed to penalties on four or more occasions within the previous two years, or the adviser interacts while subject to an ineligibility order. Cancelled penalties do not count towards the four.

A day's ordinary client work, a few calls, an email thread, a filed return, can therefore stack several separate penalties. The arithmetic escalates faster than most advisers expect, which is presumably the point.

The orders are not a discretionary extra: they are wired into the penalty ladder. Where a £10,000 penalty is assessed for repeated contraventions, section 236 obliges the officer to issue a temporary ineligibility order, effective for 12 months from the end of the 30-day period after issue. A £10,000 penalty assessed for a contravention committed while under that temporary order obliges a permanent one. Before either, HMRC must notify the adviser and allow 30 days for representations, and orders carry appeal rights alongside the penalties themselves. Section 237 provides the equivalent orders against relevant individuals personally.

Section 246 is the provision every principal should read twice. HMRC may publish the sanctioned adviser's name, including any trading name, previous name or pseudonym, a postcode, information clarifying identity, and the amount of the penalty or the type of order. The adviser gets 30 days to make representations before publication. The one-year rule cuts both ways: nothing may be published for the first time more than a year after the sanction becomes final, and published details normally come down after a year, though a permanent ineligibility order can stay up beyond it. Note that any financial penalty under the Chapter is publishable, a single £5,000 assessment included.

A fine is paid once and forgotten. A published name sits in every prospective client's search results for a year.

Procedural protections run through the regime: HMRC allows 30 days for representations before assessing a penalty, penalties must be assessed within 12 months, reasonable excuse is a defence under section 239, penalties and orders carry review and appeal rights to the tribunal under section 244, and a penalty is collected as if it were tax charged in an assessment, payable within 30 days.

The regime arrives in tranches under SI 2026/807:

Regulation 5 treats an adviser who held an Agent Services Account immediately before 18 August 2026 as registered: the application is deemed made and approved. An established practice with a live ASA did not need to do anything on commencement day. The exposure concentrates on everyone else: new entrants, overseas advisers, firms operating informally through client credentials, and anyone whose interactions with HMRC never ran through an ASA.

Abstract definitions earn their keep only at the edges, so here are three cases a practice might meet this autumn. Each turns on a specific provision, and each has a different answer. All three share one exit: register, and the compliance notice is treated as withdrawn.

A bookkeeping firm in Valletta prepares and files UK Self Assessment returns for British expatriates. No UK office, no UK staff. Section 223's extraterritorial reach puts the firm squarely inside the regime: the clients' tax affairs are UK tax affairs, and filing a return is a listed interaction. If the firm never held an Agent Services Account, the transitional rule offers no shelter, and its first post-notice filing after commencement carries a £5,000 price tag. The firm's tranche date depends on what accounts it holds, which is itself a question worth answering from the SI rather than from instinct.

A payroll software house's support team routinely contacts HMRC to untangle customers' submission failures. Schedule 20 carves out providers of payroll, tax and accounting software, so much of this activity sits inside an exception. The carve-out has edges, though: an adviser-style intervention in a specific client's tax position is a different activity from supporting a software product. The desk that drifts from one into the other drifts into the definition, and the schedule, read carefully, is the only reliable map of where that line runs.

A recently retired partner keeps helping three long-standing clients with their returns, invoicing modestly through a personal service company. The business test is met: assistance with tax affairs, in the course of a business. Retirement ended the firm's cover, and the personal company holds no ASA. Every post-notice call to HMRC on those three files is a separate £5,000 event. The kind favour that outlives the practice is, under this regime, the most expensive kind there is.

The registration rules add one more layer to a trend this blog has tracked all year: HMRC converting administrative expectations into enforceable, automated, published consequences. The response that works is procedural hygiene backed by accurate answers.

Questions arrive at the boundary constantly. Does a one-off paid favour cross the business test? Is a particular portal message an interaction in relation to a client's tax affairs? Does a Schedule 20 exception cover a software house's support desk? These are precisely the questions where a confident guess is dangerous and a cited answer earns its keep. An AI tax research tool built on primary sources can pull the section, the schedule and the commencement regulation in one pass; we publish our accuracy benchmark so you can judge how often that answer stands up, and our limitations page is equally plain about where professional judgement must take over.

For a wider framework on evaluating research tools against this kind of fast-moving statutory change, see our guide to choosing AI tax research software, and the standards behind every answer in our sources and update policy.

Registration itself is not the story; most established firms passed through commencement day without noticing, carried by the ASA transitional rule. The story is the sanctions architecture now standing behind a formality: per-interaction penalties, escalation for repeat offenders, ineligibility orders, and a public register of the sanctioned with a 30-day fuse. Regimes like this reward the firms that read them early and punish the ones that learn about them from a compliance notice.

Check your status, check your referral network, and put the statute behind every boundary question. If your practice wants cited answers to questions like these in minutes rather than research afternoons, create a GAIN Tax account.

When did tax adviser registration sanctions start? 18 August 2026 for the main adviser population, under SI 2026/807. Further tranches follow on 18 November 2026, 18 February 2027 and 1 April 2027.

How much is the penalty for an unregistered adviser interacting with HMRC? £5,000 per prohibited interaction after HMRC serves a compliance notice, rising to £10,000 per interaction once an adviser has been assessed to penalties on four or more occasions within two years, or acts while under an ineligibility order. Several penalties assessed together count as one occasion.

Do I need to register if I already have an Agent Services Account? An adviser who held an ASA immediately before 18 August 2026 is treated as registered under the transitional rule. Confirm your status rather than assuming it, particularly after any restructuring.

Can HMRC really publish my name? Yes. Section 246 of the Finance Act 2026 permits publication of a sanctioned adviser's name, trading names, pseudonyms, postcode and penalty details, after a 30-day representations window, normally for up to one year. Permanent ineligibility orders can remain published longer.

Does the regime apply to advisers based outside the UK? Yes. The prohibition applies even where the adviser and the client are both outside the United Kingdom, provided the interaction concerns a client's UK tax affairs.

Is there a defence? Reasonable excuse, under section 239. HMRC must also assess penalties within 12 months, and there are 30-day representation windows before ineligibility orders and before publication. An excuse that has ended still protects the adviser where the contravention is remedied without unreasonable delay after it ceased.

What should a firm do first? Confirm the firm's own registration status, map every person and credential that touches HMRC, and check the registration position of referral partners. Each check takes minutes now and removes a five-figure risk later.