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Sustainability requirements for suppliers: what your buyers can ask of you
Sustainability requirements for suppliers come from two places. Your customers ask for EcoVadis ratings, Scope 3 data and ESG questionnaires. The law asks for some things outright, such as ESOS and a modern slavery statement. Here is which ones apply to a UK supplier, who asks, and what each takes.
| Requirement | Who asks | Required by law? | How often | What it takes |
|---|---|---|---|---|
| EcoVadis rating | Large private customers with supplier sustainability programmes | No, but often written into contracts | Every 12 months | Policies, evidence and a questionnaire, scored by EcoVadis analysts |
| Scope 3 data | Customers with their own emissions targets or reporting duties | No | Yearly | A measured carbon footprint, split per customer or per product |
| Science-based target | Customers with SBTi targets of their own | No | Set once, reported yearly | A footprint, a reduction target and SBTi validation |
| Carbon Reduction Plan | Central government and the NHS | Only to bid for in-scope contracts | Updated yearly | A published plan in the government format, signed off by a director |
| ESOS | The regulator | Yes, for large undertakings | Every four years, with yearly updates | An energy audit, a lead assessor's sign-off and an action plan |
| ISO 14001 | Tender frameworks in construction, facilities, engineering and the public sector | No | Audited yearly, recertified every 3 years | An environmental management system and a certification audit |
| ESG questionnaires | Customers using CDP, Sedex, IntegrityNext, Achilles or their own forms | No | Mostly yearly | The same evidence base, reformatted each time |
| Modern slavery statement | The law, and customers checking it | Yes, from £36m turnover | Every financial year | A board-approved statement linked from your homepage |
Which requirements apply to my business?
Work down these questions. The first two are legal duties; the rest depend on who you sell to.
- 250 or more employees, or turnover above £44m and a balance sheet above £38m? You're a large undertaking for ESOS. Phase 4 counts the position on 31 December 2026.
- Turnover of £36m or more, including subsidiaries? You need a modern slavery statement every financial year.
- Bidding for central government contracts worth more than £5m a year? You need a Carbon Reduction Plan. Most NHS tenders ask for one too.
- Has a large customer sent an EcoVadis invitation or an ESG questionnaire? It isn't law, but the contract may depend on it.
- Does a key customer have a science-based target? Expect requests for your Scope 3 data and, before long, a target of your own.
The minimum evidence most suppliers need
Whatever arrives first, the same documents come up again and again: 12 months of energy and fuel data, a signed environmental policy, health and safety, anti-bribery and whistleblowing policies, a supplier code of conduct, training records, and any certificates you hold. Keep them in one place with a named owner and most requests become a matter of reformatting.
EcoVadis rating
EcoVadis is the request suppliers meet most often. It scores four themes (environment, labour and human rights, ethics, sustainable procurement) from the policies and evidence you upload. The scorecard lasts 12 months, so the request comes back every year.
It is a rating, not a certificate. There is no pass mark: your customer compares your score with its own threshold and with your competitors. Our guide to EcoVadis certification explains how the score and medals work, and our EcoVadis consultant service sets out our fixed fees.
Scope 3 data
Your emissions are part of your customer's Scope 3. When a large customer reports or sets targets, it needs real numbers from its main suppliers instead of spend-based estimates. The question behind every request is the same: what share of your emissions belongs to us?
Answering it means measuring your own emissions, then splitting them per customer or product in a way you can defend. Once the method exists, it repeats each year at much lower cost. Our guide to Scope 3 for suppliers covers what to send. Our Scope 3 consultant page explains how we do it and what it costs.
Science-based targets
More customers now ask whether you have a target validated by the Science Based Targets initiative (SBTi). A simpler SME route exists, and a supplier with more than 250 staff can still use it if it meets SBTi's other size and emissions tests. SBTi's new Corporate Net-Zero Standard takes over for all new submissions from February 2028. Our page on SBTi and Carbon Reduction Plan support covers both routes.
Carbon Reduction Plan (PPN 006)
Under PPN 006, central government departments, their executive agencies and non-departmental public bodies ask bidders for contracts estimated above £5 million a year, including VAT, to publish a Carbon Reduction Plan. Buyers apply it where it is relevant and proportionate to the contract. PPN 006 covers procurements started under the Procurement Act 2023 from 24 February 2025; older ones still follow PPN 06/21.
The plan commits to net zero by 2050 at the latest, reports Scope 1, Scope 2 and five Scope 3 categories, is signed off by a director and is linked from your homepage.
The NHS runs its own regime. Since April 2024 it has asked for a Carbon Reduction Plan on all new procurements, scaled to the contract. From 1 April 2027 new NHS rules ask suppliers on contracts of £5m or more a year to cover all relevant Scope 3 emissions. NHS Supply Chain frameworks also expect Evergreen Level 1, and since 1 April 2026 the Level 1 questions must be answered for an Evergreen submission to be accepted. Our NHS Evergreen guide explains each level.
ESOS
The Energy Savings Opportunity Scheme is a legal duty for large undertakings across the UK, though not in the Republic of Ireland. Phase 4 notifications are due by 5 December 2027, an action plan follows a year later, and a registered lead assessor normally has to sign off the audit. Our ESOS consultant page has the full timeline.
ISO 14001
ISO 14001 is a certified environmental management system, and many frameworks and tenders ask for it outright. Certification needs an external audit, with surveillance audits each year and recertification every three years. A new edition, ISO 14001:2026, was published in April 2026. If you need both EcoVadis and ISO 14001, plan them together: much of the evidence overlaps. See our ISO 14001 consultant service.
ESG questionnaires
CDP, Sedex, IntegrityNext, Achilles and customers' own spreadsheets all ask versions of the same questions. The efficient answer is one organised evidence base, with a named owner, that every questionnaire draws from. Our supplier sustainability assessment guide compares the main ones. See CDP for suppliers if you have had a request.
Modern slavery statement
Under section 54 of the Modern Slavery Act 2015, an organisation that carries on business in the UK, supplies goods or services and has total turnover of £36 million or more, including its subsidiaries, must publish a statement every financial year. The board approves it, a director signs it, and it is linked from your homepage. Customers check it, and EcoVadis looks for the human rights due diligence behind it. A Bill to make the content mandatory and add penalties was before Parliament in 2026, so watch for changes.
What this could earn you. Each requirement makes you gather energy, materials, waste and supplier data in one place. That same data often shows where money is leaking out of the business.