Fractional CSO

Fractional Chief Sustainability Officer (CSO) Recruitment

Exec Capital provides fractional Chief Sustainability Officer recruitment for UK mid-market businesses, scale-ups and PE-backed portfolios that need board-level sustainability leadership without the cost of a full-time appointment. On this page, CSO means Chief Sustainability Officer: the executive who owns sustainability strategy, climate and ESG reporting, and the board’s oversight of environmental and social risk. Permanent CSO packages at listed and large private companies are set at C-suite level, and for many businesses with annual turnover under £250m that cost structure is rarely justified — but the regulatory and investor pressure to demonstrate credible sustainability governance is no smaller than it is at FTSE 100 level.

Looking for a Chief Strategy Officer rather than a Chief Sustainability Officer? See our Head of Strategy and Chief Strategy Officer recruitment page.

A fractional CSO engagement — typically two to four days per month with the executive attending board meetings, owning the sustainability strategy, leading climate-related financial disclosure, chairing the sustainability committee and engaging investors and customers on ESG matters — provides senior sustainability capability for a fraction of the cost of a full-time appointment. Exec Capital maintains a network of experienced fractional CSOs across mid-market, FTSE 250 and PE-backed backgrounds, and we also place fractional heads of sustainability where the business needs senior delivery more than a board title.

How a Fractional CSO Search Works

A fractional appointment is a smaller commitment than a permanent hire, but the person still sits in front of your board, your investors and your auditors. We run the search with the same discipline as a full executive search, scaled to the role. We agree the timetable with you at briefing; it depends on how specialist the brief is and how quickly your interview panel can meet.

Why Businesses Engage a Fractional Chief Sustainability Officer

The fractional CSO model fits a particular business profile: organisations with board-level sustainability accountability but without the scale to justify full-time C-suite compensation. Typical engagement scenarios:

Ongoing board-level sustainability oversight. A mid-market business with statutory disclosure obligations (SECR, TCFD-aligned climate disclosures) and customer or investor ESG expectations needs ongoing senior sustainability leadership to chair the sustainability committee, brief the board on emerging risks, and ensure annual disclosures meet auditor and regulator expectations. A fractional CSO at three days per month provides this oversight without the full-time cost.

Sustainability strategy ownership. Setting and reviewing the corporate sustainability strategy, science-based target trajectories, and net zero roadmap is fundamentally a board-level activity. A fractional CSO owns this work — typically with quarterly board reporting, annual strategy review and ongoing engagement with the executive team on delivery.

Investor and customer ESG engagement. Where investors (PE sponsors, institutional shareholders) or major customers (large corporates with supply chain emissions commitments) require structured ESG engagement, a fractional CSO provides the senior point of contact, manages the diligence response, and represents the business credibly in stakeholder conversations.

PE-backed portfolio sustainability oversight. PE sponsors increasingly require portfolio companies to demonstrate credible sustainability governance, particularly in advance of exit. A fractional CSO can serve a single portfolio company or, in some arrangements, multiple portfolio companies within the same fund — providing consistent sustainability leadership across the portfolio. Our guide to how fractional executives fit into PE-backed firms covers the sponsor’s side of that arrangement.

Audit and assurance preparation. Annual sustainability assurance (limited or reasonable) is becoming the norm for mid-market businesses. A fractional CSO owns the assurance relationship, prepares the reporting boundary, and engages with the assurance provider on findings and remediation.

A part-time head of sustainability where there is no team. Many businesses search for a “part-time head of sustainability” because the work exists but nobody owns it: the carbon footprint is calculated by a consultant, the customer questionnaires are answered by whoever has time, and the annual report wording is drafted by the finance team. A fractional CSO, or a fractional head of sustainability below board level, gives that work an owner and a plan, and decides which pieces should be built in-house and which bought in.

Regulatory and Reporting Drivers for Fractional CSO Demand

Statutory sustainability reporting has expanded significantly over the last five years, and most mid-market UK businesses now operate in scope of at least one of the following frameworks:

SECR (Streamlined Energy and Carbon Reporting). The UK SECR regime requires quoted companies and large UK unquoted companies and LLPs to disclose energy use and carbon emissions in their annual reports. “Large” follows the Companies Act size tests: for financial years beginning on or after 6 April 2025 the turnover and balance sheet thresholds rose to £54m and £27m (from £36m and £18m), with the 250-employee test unchanged, and a company is large if it meets two of the three. Some businesses have dropped out of scope as a result, but most continue to report voluntarily because customers and lenders still ask for the numbers — and this is exactly the scale where a fractional CSO is the right structural fit.

TCFD-aligned disclosure. The Task Force on Climate-related Financial Disclosures itself was disbanded in October 2023, with the ISSB taking over the monitoring of company climate reporting, but its four-pillar framework (governance, strategy, risk management, metrics and targets) remains embedded in UK law. The Companies Act climate-related financial disclosure rules apply to traded companies, banks, insurers and AIM companies with more than 500 employees, and to private companies and LLPs with more than 500 employees and turnover above £500m. The framework requires senior executive ownership to coordinate cross-functional input.

ISSB IFRS S1 and S2. The International Sustainability Standards Board’s general sustainability (IFRS S1) and climate (IFRS S2) standards have been endorsed for UK use as the UK Sustainability Reporting Standards, UK SRS S1 and UK SRS S2, published by the Government on 25 February 2026. They are voluntary for most companies; any wider mandatory use depends on further Government decisions. Businesses preparing to disclose under UK SRS need executive-level sustainability leadership to manage the readiness process, because S1 reaches beyond climate into every sustainability-related risk and opportunity that could reasonably affect the business’s prospects.

FCA listing rules move from TCFD to UK SRS. In PS26/19, published on 30 September 2026, the FCA replaced its TCFD-aligned climate reporting rules for listed companies with disclosures against UK SRS on a comply-or-explain basis. The new rules apply to accounting periods starting on or after 1 January 2027, so first reports land in 2028, with one year of transitional relief for Scope 3 emissions and two years for the wider UK SRS S1 disclosures. Listed businesses that have relied on a light-touch TCFD statement now need someone senior to plan the step up.

FCA Sustainability Disclosure Requirements. The FCA’s SDR and investment labelling framework applies to UK asset managers and the labelling of sustainable investment products. Investment management businesses building sustainable fund ranges typically need sustainability expertise at executive level. The FCA’s anti-greenwashing rule, in force since 31 May 2024, also applies to every FCA-authorised firm that makes sustainability claims about its products or services, which means the compliance function and the sustainability lead have to work together. Regulated firms that need compliance cover alongside sustainability leadership often pair a fractional CSO with a fractional Chief Compliance Officer or a fractional compliance officer holding SMF16.

EU CSRD extraterritorial reach. The EU Corporate Sustainability Reporting Directive applies to UK businesses with significant EU operations, EU subsidiaries above thresholds, or UK parents of EU-domiciled entities. CSRD reporting is materially more comprehensive than UK domestic regimes. The EU’s Omnibus simplification package has narrowed its scope considerably: EU companies and groups are now in scope at 1,000 employees and €450m net turnover, and non-EU parents, including UK groups, only where they have more than €450m of EU turnover, with their reporting starting from financial year 2028. Fewer UK mid-market businesses are caught, but those that are need to plan well ahead.

Companies Act and FRC expectations. Directors’ statutory duty to have regard to environmental impact under section 172, alongside the Financial Reporting Council’s annual report expectations, increasingly require boards to demonstrate active oversight of sustainability strategy and risk.

When to Engage Fractional Rather Than Permanent or Interim

The fractional model differs from both permanent CSO recruitment and interim engagement. The choice between the three depends on scale, scope and engagement duration:

Scale below permanent threshold. A business with turnover under £250m that wants ongoing senior sustainability leadership often cannot justify a full-time CSO on a C-suite package. A fractional engagement at three days per month provides board-level sustainability ownership at a fraction of that cost — a meaningful difference in cost structure for an organisation at that scale.

Ongoing relationship rather than defined programme. An interim CSO engagement typically runs six to twelve months with a defined endpoint — CSRD readiness, net zero strategy design, function build-out. A fractional CSO engagement is open-ended, supporting the business’s ongoing sustainability work across years rather than a single programme.

Days per month, not days per week. Interim CSOs are typically full-time engagements (four to five days per week). Fractional CSOs work two to four days per month, often spread across multiple businesses. The two engagement models suit different operational rhythms.

Multiple stakeholder boards. Some fractional CSOs work across multiple PE portfolio companies or trade between three or four mid-market boards, bringing pattern recognition from comparable situations. Interim and permanent models do not support this multi-board working arrangement.

When permanent is the right answer. If sustainability is central to the business model — a large manufacturer with heavy Scope 1 and 2 emissions, a listed company facing full UK SRS reporting, an asset manager whose products carry sustainability labels — the work usually outgrows a few days a month. At that point a permanent appointment through our Chief Sustainability Officer recruitment service is the better fit, and a fractional CSO can help write the brief and hand over.

Fractional CSO vs Interim CSO vs ESG Consultancy vs Permanent CSO

Most businesses weighing a fractional CSO are also looking at three alternatives: an interim executive, an ESG consultancy, or a permanent hire. They are not interchangeable. The table sets out how they differ in practice.

Many of the businesses we speak to already use a consultancy and find that the work is good but nobody inside the business owns it. A fractional CSO does not replace the consultancy so much as manage it: deciding what to commission, challenging the output, and turning reports into decisions the board can take. Equally, where the requirement is genuinely a one-off — a single carbon baseline or a materiality exercise — a consultancy may be all you need, and we will say so.

Skills, Profile and Day-Rate Expectations

The effective fractional CSO combines deep sustainability expertise with the operational discipline to work productively within a constrained time allocation. The profile that works in this market includes:

Reporting framework fluency. Direct experience delivering disclosures under SECR, TCFD, ISSB and UK SRS and, where relevant, CSRD. The fractional must operate independently — there is rarely a deep internal sustainability team to lean on at mid-market scale.

Board-level governance experience. The fractional CSO presents to the full board, audit and risk committee, and engages directly with the Chair. Prior board exposure is the prerequisite — fractional engagements provide no time for ramp-up on board operating practice.

Time discipline. Working three days per month at a board-level role requires unusual operational discipline — clear meeting agendas, efficient working sessions, structured handovers to internal teams. Candidates without prior fractional or non-executive experience often struggle to operate within the time allocation.

Sector relevance. Consumer-facing businesses, B2B service organisations, manufacturing, financial services and real estate each have distinct sustainability profiles. Sector-relevant prior experience is a strong indicator of fast time-to-impact in a fractional engagement.

Commercial and financial fluency. Sustainability decisions are increasingly capital allocation decisions: a decarbonisation plan has a cost, a payback and a financing route. The best fractional CSOs can sit with the CFO and build the business case, and understand how climate risk feeds into impairment testing, going concern and viability statements. Our Chief Sustainability Officer job description sets out the full range of responsibilities a CSO may carry.

Compensation and Package Structure

Fractional CSOs are paid a day rate for an agreed number of days per month, sometimes with a monthly retainer covering a set allocation and a separate rate for additional days. There is no salary, bonus, pension or benefits package, and no employer’s National Insurance where the executive is engaged outside the payroll. The rate is driven by four things:

• Scale and complexity of the business. A single-site UK business with SECR reporting needs a different profile from an international group facing UK SRS, CSRD and customer supply chain demands.
• Regulatory exposure. Listed companies, FCA-regulated firms and businesses with EU reporting obligations draw on a smaller pool of executives with direct experience, which is reflected in the rate.
• Board responsibility. A fractional CSO who chairs a committee, signs off disclosures or holds a statutory directorship carries more personal exposure than one who advises the executive team.
• Days per month and flexibility. Low day counts with tight deadlines around reporting season are harder to schedule than a steady allocation spread across the year.

When we put a fractional CSO forward, the day rate we quote includes our fee, so you see one figure for the engagement. We give you current rates for your brief at the briefing stage rather than publishing general figures, because they vary widely with the factors above. For permanent comparisons, our C-suite salary guide covers how senior executive packages are structured.

IR35. Most fractional CSOs work through their own limited company, so the off-payroll working rules apply. If your business is medium or large, you decide the executive’s IR35 status and issue a status determination statement; if it is small, the executive’s company makes that assessment. The Companies Act size thresholds rose for financial years beginning on or after 6 April 2025, but HMRC’s April 2025 Employer Bulletin says this has no practical impact for off-payroll working until 6 April 2027 at the earliest. Our guide to IR35 for senior executive engagements covers the practical points, and we can discuss how the engagement is structured at the offer stage.

What a Fractional CSO Typically Delivers in the First 90 Days

A fractional CSO working a few days a month cannot do everything at once, so the first three months are about establishing where the business stands, what it must do, and in what order. A typical first 90 days looks like this:

Month one: diagnosis. Review the last annual report, any SECR and climate disclosures, the carbon footprint methodology and the customer and investor questionnaires already answered. Meet the CEO, CFO, Chair and the people who currently hold pieces of the work. Confirm which regimes the business is in scope of now and which it is likely to be in scope of within two or three years, including UK SRS through the listing rules or a customer’s supply chain requirements.

Month two: priorities and governance. Produce a short gap analysis and a prioritised plan: what must be fixed for the next reporting cycle, what can wait, and what is optional. Propose the governance — whether a sustainability committee is needed, how it relates to the audit and risk committee, and what the board sees and when. Agree data ownership with finance and operations so that emissions and other metrics are collected with the same control as financial numbers.

Month three: first board paper and quick wins. Present the plan to the board with clear decisions to take: targets, budget, consultancy spend and any hires. Close the obvious gaps — a sustainability policy that matches what the business actually does, consistent answers to customer questionnaires, a check of marketing and product claims against greenwashing risk — and set the calendar for the year ahead.

By the end of the first quarter, the board should know where the business stands, what it is committing to, and who is doing what. From there, the fractional CSO settles into a steady rhythm around the board calendar and the reporting cycle, with more days in the run-up to year-end disclosures and fewer in quieter months.

How to Assess a Fractional CSO at Interview

Sustainability is a field where titles and vocabulary travel faster than experience. Two candidates can describe the same frameworks in the same words while one has signed off disclosures in front of auditors and the other has only contributed a section. The interview needs to separate the two. These are the questions we find most useful, and the ones we test before a candidate reaches your shortlist:

• “Walk me through the last disclosure you owned.” Listen for who signed it off, how the data was controlled, what the assurance provider challenged and what changed as a result. Vague answers about “supporting” a report suggest a contributor rather than an owner.
• “How do you run this role in three days a month?” A good fractional CSO will describe a working rhythm: a fixed board slot, a monthly session with the CFO, clear owners for data collection, and a short written update between visits. Candidates who have only held full-time roles often underestimate this.
• “Where have you said no?” Part of the job is telling the business that a claim cannot be supported, a target is not credible or a consultancy proposal is more than it needs. Ask for an example.
• “What would you do first here?” Give the candidate your last annual report or sustainability statement in advance. Their first view tells you more about judgement and sector understanding than any competency question.
• “Who else are you working with?” Fractional executives hold several roles. Check for conflicts with competitors or customers, and make sure their diary leaves room around your reporting season.

We also take references from people who have worked with the candidate in a fractional or board setting, not only from former line managers, because the fractional role depends on influencing a leadership team the CSO does not manage day to day. Where a candidate will hold a statutory directorship or a regulated role, we add the checks that appointment needs. The aim is a shortlist where every candidate could do the job, so that your decision comes down to fit with your board and your business.

Engagement and Fees

We agree the fee structure with you at the briefing, based on the type of appointment and how the search will be run. In outline:

• Fractional and interim appointments are charged on a day-rate basis. The day rate we quote includes our fee, and you are invoiced for the days worked.
• Permanent appointments can be run on a retained or contingent basis depending on how specialist the brief is and how much market mapping it needs. Our guide to retained versus contingent executive search explains the difference.
• What is included: the brief, the search and approach, candidate assessment and referencing, the shortlist write-ups, interview co-ordination, offer negotiation, and contact through the early months of the engagement.

If the fractional engagement later turns into a permanent role, we discuss how that is handled at the outset so there are no surprises. Our article on replacing fractional executives with full-time hires covers how businesses plan that transition.

Who We Place Fractional CSOs With

Fractional sustainability leadership suits a wide range of businesses. The common thread is a real and growing set of sustainability obligations without the volume of work for a full-time executive. Typical clients include:

• PE-backed portfolio companies where the sponsor expects ESG reporting to the fund and wants sustainability credentials in good order before exit.
• Owner-managed and family businesses whose major customers now require emissions data, targets and supply chain commitments as a condition of tender.
• Manufacturing, logistics and construction businesses with significant direct emissions, energy costs and decarbonisation decisions to make.
• Smaller listed and AIM companies preparing for disclosures against UK SRS and investor stewardship questions.
• Asset managers and other FCA-regulated firms dealing with SDR, product labels and the anti-greenwashing rule.
• Real estate, consumer brands and B2B services facing tenant, consumer or client scrutiny of their environmental claims.

If your business needs a board-level sustainability voice rather than an executive, a non-executive director with sustainability experience may be the right route; see our non-executive director recruitment service.

Sustainability leaders looking for fractional work. If you are an experienced CSO or head of sustainability building a fractional portfolio, please register with us and see our current opportunities.

Other Ways to Hire a Chief Sustainability Officer

This page covers fractional appointments. If a different format suits you better, our sibling services cover each one: CSO recruitment for permanent Chief Sustainability Officer searches; interim CSO search (above) for full-time, fixed-term programmes; and Sustainability Director recruitment where the role sits below the executive committee. If you are still deciding which route fits, our guide to hiring a Chief Sustainability Officer walks through the options, and you can contact us to talk it through.

Frequently asked questions

What is a fractional Chief Sustainability Officer?

A fractional Chief Sustainability Officer is a senior sustainability executive who works for a business part-time on a continuing basis, usually a few days a month. They own the sustainability strategy, climate and ESG reporting, and the board’s oversight of sustainability risk, in the same way a full-time CSO would, but with the time allocation matched to the size of the job.

Does CSO mean Chief Sustainability Officer or Chief Strategy Officer?

Both titles are in use. On this page, and across our fractional CSO, interim CSO and CSO recruitment pages, CSO means Chief Sustainability Officer. For Chief Strategy Officer searches, see our head of strategy recruitment page linked at the top of this page.

How many days a month does a fractional CSO work?

Most engagements are two to four days a month, with extra days around board meetings and the annual reporting cycle. The allocation is agreed at the outset and reviewed as the business’s needs change.

Is a part-time head of sustainability the same as a fractional CSO?

They overlap. A fractional CSO usually holds executive-level accountability and reports to the board; a part-time head of sustainability is more often a delivery role reporting to the CFO or COO. We place both, and the brief tells us which you need: if the board needs a single accountable owner, it is a CSO role; if the strategy is set and you need someone to run the programme, a head of sustainability may be enough.

How much does a fractional CSO cost?

You pay a day rate for the days worked. The rate depends on the size and complexity of the business, regulatory exposure and the level of board responsibility. When we place a fractional CSO, the day rate includes our fee. We share current rates for your brief at the briefing rather than publishing general figures.

Should we hire a fractional CSO or use an ESG consultancy?

A consultancy is good for defined technical projects such as a carbon baseline or materiality study. A fractional CSO is an accountable executive who owns the strategy year after year and manages any consultancy the business uses. Many businesses use both, with the fractional CSO deciding what to commission.

Do we need a CSO because of the UK Sustainability Reporting Standards?

Not necessarily. UK SRS S1 and S2 were published in February 2026 and are voluntary for most companies. Listed companies are different: under FCA PS26/19 they report against UK SRS on a comply-or-explain basis for accounting periods starting on or after 1 January 2027. Whether you need a CSO depends on your obligations, your investors and your customers as a whole, which is what the brief establishes.

Does a fractional CSO sit on the board?

Usually they attend board meetings for sustainability items and report to the board or a sustainability committee without being a statutory director. Some businesses appoint them to the board; if so, the directors’ duties and insurance cover need to be addressed. Our article on insurance and liability for fractional leaders covers the points to check.

How is a fractional CSO engaged for IR35 purposes?

Most work through their own limited company. Medium and large clients must assess IR35 status and issue a status determination statement; for small clients the executive’s company makes the assessment. We discuss the structure with you at the offer stage.

Can a fractional CSO become a permanent hire?

Yes. Some businesses start fractional and convert when the workload grows; others use the fractional CSO to build the function and help recruit a permanent successor. We agree how a conversion would be handled before the engagement starts.

Related Services

Interim CSO | Sustainability Director Recruitment | Chief Sustainability Officer Job Description | Fractional CEO | Fractional CFO | Fractional COO | Fractional CMO | Fractional CTO | Fractional CIO | Fractional Finance Director | Fractional HR Director | Fractional Managing Director