Sustainability advisory for UK accounting firms: what the service actually is, and where the demand sits

Sustainability advisory, when an accounting firm delivers it, is the work of helping SME clients measure their carbon footprint, develop credible reduction plans, and produce the sustainability data that customers, lenders, and tender processes are increasingly asking for. It sits next to existing compliance and advisory work rather than as a separate specialism. The demand for it is shifting from gradual to active.

The substantive question for partners considering it as a service line is narrower than the broader conversation around sustainability tends to allow. What does the service actually contain? Where is the demand coming from at SME level, and at what scale? And what does it take to build the capability without overcommitting to something that might still take three years to fully mature?

What the service actually contains

Sustainability advisory in an accounting context is not consulting on environmental philosophy. It's a defined set of client conversations that produce specific deliverables, most of which sit naturally next to existing compliance and advisory work.

The work falls into a few practical categories. Helping a client measure their current carbon footprint, usually starting with the categories most likely to be requested by customers or lenders. Building a credible reduction plan with prioritised actions and a defined timeline, of the kind now required for any UK public sector contract above £5 million. Producing the structured sustainability data that larger customers are increasingly requesting as a condition of doing business. Helping the client work out which of these things matter for their specific commercial position and which can wait.

None of that requires reinventing the firm. It requires knowing the framework well enough to lead the conversation, having a repeatable process for delivering it, and being willing to charge for it as a distinct service rather than absorbing it into general advisory.

Where the demand is coming from

The demand picture for SME sustainability advisory has shifted noticeably over the past two years. Most of the change is driven by commercial pressure rather than regulation, which matters because commercial pressure tends to produce faster client decisions than regulatory deadlines do.

The British Business Bank's 2025 SMEs and Net Zero report, drawing on a survey of 1,783 UK SMEs, found that 37% of medium-sized businesses, 20% of small businesses and 8% of microbusinesses had been asked by customers for carbon data in the previous twelve months. Among large UK organisations, 51% reported receiving such requests from customers or in tender applications, rising to 62% among exporters. The pressure is moving down the supply chain at a measurable rate.

Two structural factors are accelerating this. The UK Sustainability Reporting Standards, finalised by the government in February 2026, will require larger companies to disclose their Scope 3 emissions, which means asking suppliers for the underlying data. Separately, the UK Procurement Act, in force from February 2025, embeds sustainability criteria across public sector tenders, with Carbon Reduction Plans now required for all contracts above £5 million. SMEs sitting in either of those pipelines are going to be asked questions they don't currently have answers to.

To take a specific example, PSI, an events and lighting business advised by The Green Accountants, found themselves being asked for carbon reduction plans and having ESG questionnaires put in front of them when bidding for tenders. The questions weren't unmanageable, but they weren't ones the company had the in-house data or framework to answer confidently on its own. PSI worked with their accountant to build a credible carbon reduction plan and a repeatable way of responding to supplier questionnaires. The accountant, in turn, picked up a recurring advisory engagement that didn't exist a year earlier. That sequence is becoming familiar across multiple sectors.

The other strand is the commercial case for the SMEs themselves. The government-backed Willow Review, published in June 2025, found that among SMEs already adopting sustainable practices, 67% reported reduced operational costs and 53% reported access to new customers. The financial benefits are real, but they're unevenly recognised across the SME population, and that recognition gap is essentially the space where sustainability advisory produces its commercial value. Clients don't yet know what they don't know, and someone has to translate.

Where UK firms currently sit

UK accounting firms have noticed the demand but most have not yet built the capability to meet it. ICAEW's 2025 Evolution of Mid-Tier Accountancy Firms research, surveying 36 UK mid-tier firms, found that 44% plan to introduce ESG-related services within the next three years. That's a substantial jump from the previous year's research, when only 10% saw ESG as a growth opportunity. The sample is small and worth treating accordingly, but the direction matches what the broader SME data shows.

Of the firms not planning to introduce ESG services, two-thirds cited lack of expertise and resources rather than lack of demand. That's a useful detail, because it tells you what the actual barrier is. The opportunity is identified, the client appetite exists, but the operational capability hasn't been built yet.

Smaller independent practices, which dominate the UK market and serve most of the SME base, aren't separately surveyed in the ICAEW research. They appear to be moving more cautiously, partly because they have less spare capacity to develop new service lines and partly because their clients sit further down the supply chain than the mid-tier client base. That cautious posture is reasonable, but it shouldn't be confused with the demand not arriving. The demand is arriving. It's just arriving later, and via slightly different routes.

Why the timing is unusual

The combination of factors making the next eighteen months an unusual entry window for sustainability advisory is worth being explicit about, because most service line decisions don't have this kind of timing dimension.

Compliance work is being compressed by AI, which means advisory revenue needs to fill the gap. Sustainability advisory is one of the few advisory areas with clear external pressure already driving client demand, set against a relatively manageable barrier to entry compared with specialisms like corporate finance or M&A. The frameworks are stabilising rather than still in flux. Clients are beginning to ask the questions, which is the hardest piece of any new service line to manufacture.

Firms entering the market in 2026 don't need to move dramatically. They need to be able to lead a credible client conversation by the time those conversations start arriving in volume, which on current trajectories is likely to be 2027 to 2028. Building the capability now means having a saleable service when the demand peaks rather than scrambling to acquire it after.

How firms tend to start

The firms making progress on sustainability advisory aren't doing anything especially clever. The pattern is fairly consistent across early movers.

Technical knowledge comes first, usually through accredited training that gives the team the vocabulary and the confidence to lead client conversations without bluffing. A repeatable process gets built around those conversations, with templates, engagement letters and a defined deliverable, so the work doesn't have to be reinvented every time. Pilot delivery happens with a small number of existing clients, usually those with the most obvious supply chain or procurement exposure, before any wider go-to-market push.

Starting before you feel completely ready is, in practice, the only way it happens. The frameworks will continue to evolve. The technical detail will look different in three years than it does now. Waiting for perfect knowledge in a fast-moving area means waiting indefinitely, by which point clients have either solved the problem with someone else or worked around their accountant entirely.

What gets a firm most of the way there is professional credibility plus working knowledge of the framework, applied to clients who already trust the firm's judgement on commercial questions. That combination is genuinely difficult to replicate once another adviser has it. Sustainability advisory engagements, like most advisory relationships, are sticky in a way that compliance work is not.