TL;DR
Scope 3 emissions are all the indirect greenhouse gas emissions that occur across a company's value chain, outside its own operations. For most businesses, they are the largest share of the total carbon footprint and the hardest to measure. Here is what you need to know:
-
What they are: All indirect emissions not covered by Scope 1 or Scope 2, organised into 15 categories under the GHG Protocol
-
Why they matter: Scope 3 can account for 80-95% of a company's total value-chain emissions, according to the UK government's call for evidence on Scope 3 reporting
-
Where to start: Run a materiality assessment or hotspot screen to identify which categories are most significant for your business – do not try to measure everything at once
-
What comes next: Prioritise reducing emissions in material categories, then consider where carbon credits may support a broader net-zero strategy for residual emissions
What are Scope 3 emissions?
Scope 3 emissions definition: Scope 3 emissions are all indirect greenhouse gas emissions that occur in a company's value chain and are not included in Scope 2. They cover both upstream activities (such as the production of purchased goods and services) and downstream activities (such as the use and disposal of products a company sells). Scope 3 is defined and standardised by the GHG Protocol Corporate Value Chain (Scope 3) Standard, the only internationally accepted methodology for accounting for these emissions.
Together, Scope 1 emissions (direct emissions from owned sources), Scope 2 emissions (indirect emissions from purchased energy), and Scope 3 emissions form a complete picture of a company's greenhouse gas footprint. Scope 3 is the broadest category by far.
The key distinction is control versus influence. A company controls its Scope 1 and 2 emissions directly. Scope 3 emissions occur at sources owned or operated by other entities in the value chain: suppliers, logistics providers, customers, employees, and investors. That is precisely what makes them both the most significant and the most challenging source of emissions for most organisations to address.
Why Scope 3 matters
For supply-chain-heavy businesses, Scope 3 is not a secondary concern. According to the UK government's call for evidence on Scope 3 emissions in the reporting landscape, Scope 3 can account for anywhere between 80% and 95% of a company's total value-chain footprint. A company that achieves significant Scope 1 and 2 reductions but ignores its supply chain emissions may be addressing less than 20% of its actual climate impact.
The real risk: companies that build net-zero strategies without Scope 3 data are setting targets against an incomplete baseline. That creates credibility problems with investors, customers, and regulators as disclosure expectations tighten.
| Why teams delay Scope 3 | Why it matters now |
|---|---|
| Data sits outside direct control | Supply chain emissions dominate most footprints |
| No single mandatory UK requirement yet | UK SRS S2 and CSRD are raising expectations fast |
| Supplier data is inconsistent or unavailable | Incomplete data still reveals material hotspots |
| It feels like a reporting exercise | Better data improves procurement and supplier decisions |
| Perceived cost and complexity | Spend-based screening can begin with existing finance data |
The business case is not just about compliance. Scope 3 data helps procurement teams identify high-emission spend categories, supports supplier engagement programmes, and provides the evidence base for credible science-based targets under SBTi.
The 15 Scope 3 categories
The GHG Protocol Scope 3 Standard organises all value-chain emissions into 15 mutually exclusive categories. They are designed so that emissions are not double-counted within a single company's inventory. The categories split into upstream (related to purchased goods and services) and downstream (related to sold goods and services).
Not every category will be material for every business. The table below maps each category to its type and gives a plain-English example to help teams identify which ones are likely to matter most.
| # | Category | Type | Business example |
|---|---|---|---|
| 1 | Purchased goods and services | Upstream | Raw materials, components, or professional services bought by a manufacturer or retailer |
| 2 | Capital goods | Upstream | Machinery, vehicles, or buildings purchased and used in operations |
| 3 | Fuel- and energy-related activities | Upstream | Extraction and processing of fuels and energy not covered in Scope 1 or 2 |
| 4 | Upstream transportation and distribution | Upstream | Third-party logistics moving goods to your facilities |
| 5 | Waste generated in operations | Upstream | Disposal and treatment of operational waste |
| 6 | Business travel | Upstream | Flights, rail, and hotel stays for employees |
| 7 | Employee commuting | Upstream | Employees travelling to and from work by any mode |
| 8 | Upstream leased assets | Upstream | Emissions from assets leased by the company not included in Scope 1 or 2 |
| 9 | Downstream transportation and distribution | Downstream | Third-party logistics moving finished goods to customers |
| 10 | Processing of sold products | Downstream | Further manufacturing of intermediate products by customers |
| 11 | Use of sold products | Downstream | Energy or fuel consumed when customers use a product (e.g. appliances, vehicles) |
| 12 | End-of-life treatment of sold products | Downstream | Disposal, recycling, or landfill of products after customer use |
| 13 | Downstream leased assets | Downstream | Emissions from assets leased out to customers |
| 14 | Franchises | Downstream | Emissions from franchisee operations not included in Scope 1 or 2 |
| 15 | Investments | Downstream | Emissions associated with equity investments, project finance, and debt (key for financial services) |
Which categories matter most?
The answer depends on the sector, but several categories are material for most businesses:
-
Category 1 (purchased goods and services) is typically the largest upstream category for manufacturers, retailers, and construction firms. It often represents the single biggest opportunity for supply chain decarbonisation.
-
Category 11 (use of sold products) dominates for companies selling energy-consuming products such as vehicles, appliances, or industrial equipment.
-
Category 15 (investments) is the primary focus for banks, insurers, and asset managers, where financed emissions can dwarf operational ones.
-
Categories 6 and 7 (business travel and employee commuting) are frequently material for professional services and knowledge-economy businesses.
Key insight: The GHG Protocol recommends using an initial screening exercise to prioritise categories by likely emissions size, data availability, and the company's ability to influence reductions, before committing to detailed measurement across all 15.
How to calculate Scope 3 emissions without overcomplicating it
The GHG Protocol's Scope 3 Calculation Guidance is clear on one point: companies should choose calculation methods for each category based on an initial screening exercise, not attempt a full bottom-up inventory from day one. That principle should shape how any team approaches Scope 3 for the first time.
A practical 4-step starting framework
-
Run a Scope 3 materiality assessment. Map all 15 categories against your business model and identify which are likely to be significant. Use criteria such as estimated emissions size, business relevance, stakeholder interest, and your ability to influence reductions. This is also called a hotspot analysis.
-
Prioritise 3-5 material categories. Focus initial data collection on the categories most likely to represent the majority of your footprint. For most businesses, this means starting with Category 1 and any sector-specific categories identified in step one.
-
Choose a proportionate calculation method for each category. The GHG Protocol outlines several approaches:
| Method | How it works | Best used when |
|---|---|---|
| Spend-based | Applies emissions factors to financial spend data | Starting out; supplier data unavailable |
| Activity-based | Uses physical activity data (e.g. kg of material, km travelled) | More accuracy needed; data available |
| Supplier-specific | Uses actual emissions data provided by suppliers | High-materiality categories; mature supplier programmes |
| Hybrid | Combines spend-based and activity-based approaches | Partial supplier data available |
- Document assumptions and commit to improving data quality over time. Early Scope 3 estimates are expected to rely on proxies. The UK government's sustainability reporting guidance explicitly acknowledges that Scope 3 data often lacks granularity and comparability, particularly in early reporting cycles. Documenting your methodology and improving it year-on-year is both acceptable and expected.
Key insight: A spend-based estimate using existing procurement data is a legitimate starting point. It will not be perfect, but it will reveal where the emissions are concentrated and where to focus next.
Common Scope 3 data collection challenges
Scope 3 data collection is genuinely difficult. The UK government's sustainability reporting guidance notes that Scope 3 estimates often span multiple years, rely on proxies, and lack the granularity of Scope 1 and 2 data. That is not a reason to avoid starting. It is a reason to set realistic expectations and build incrementally.
| Challenge | Practical response |
|---|---|
| Data sits across procurement, finance, HR, logistics, and travel | Assign cross-functional ownership early; no single team can do this alone |
| Supplier data is incomplete or unavailable in year one | Use spend-based estimates to start; build supplier engagement in parallel |
| Emissions factors vary by source and may not match your supply chain | Use reputable factor databases (e.g. DEFRA, EXIOBASE) and document which you used |
| Scope 3 estimates can span multiple reporting years | Be transparent about boundaries and time periods in your methodology note |
| Internal buy-in is limited because Scope 3 feels abstract | Translate emissions into spend categories and supplier tiers that procurement already tracks |
The governance point most teams miss: Scope 3 data collection is a cross-functional problem, not a sustainability team problem. Finance holds the spend data. Procurement holds the supplier relationships. Operations holds the logistics data. HR holds the travel and commuting data. Sustainability can set the methodology, but it cannot gather the data alone.
Scope 3 reporting requirements in the UK
Scope 3 reporting is not yet universally mandatory for UK companies in the same way as Scope 1 and 2 disclosures. But the direction of travel is clear, and "not mandatory yet" is not the same as "not expected."
Where things currently stand
| Framework | Who it applies to | Scope 3 requirement | Status |
|---|---|---|---|
| SECR | Large UK companies and LLPs | Voluntary for most categories; some Scope 3 included for unquoted companies | Mandatory (Scope 1 and 2 focus) |
| UK SRS S2 | Listed companies (FCA-regulated) | Comply-or-explain on Scope 3; embedded in climate disclosure requirements | Voluntary 2026; mandatory from 2027 |
| CSRD / ESRS | Large EU companies and non-EU companies above threshold | Scope 3 reporting mandatory where material | In force for largest companies; phased |
| CDP disclosure | Voluntary; requested by investors and customers | Full Scope 3 disclosure expected | Voluntary but increasingly expected |
The UK Sustainability Reporting Standards (UK SRS S2), published in February 2026 and aligned with ISSB's IFRS S2, embed Scope 3 within the climate disclosure architecture. The FCA has not proposed mandatory Scope 3 disclosure for initial implementation, citing practical data challenges, but has adopted a comply-or-explain approach. As the UK ESG regulatory landscape makes clear, mandatory adoption for listed companies is targeted from 1 January 2027.
The practical takeaway: UK companies exposed to investor scrutiny, CSRD through their EU supply chain relationships, or CDP requests cannot treat Scope 3 as optional indefinitely. Building data readiness now is significantly easier than scrambling to comply under a tighter deadline.
Scope 3 reduction strategies and supplier engagement
Measurement is not the end goal. The GHG Protocol frames Scope 3 inventories explicitly as a basis for identifying and acting on reduction opportunities. Once material categories are identified, the focus shifts to what can actually change.
Priority levers for reducing Scope 3 emissions
-
Supplier engagement: For Category 1-heavy businesses, working with key suppliers to set emissions reduction targets is the highest-impact lever. This can include setting supplier requirements in procurement contracts, running supplier data collection programmes, and prioritising lower-carbon suppliers in sourcing decisions.
-
Procurement policy: Shifting spend toward lower-emission materials, products, and services directly reduces Category 1 and 2 emissions.
-
Product and service design: Designing products for lower energy use in operation reduces Category 11 (use of sold products) emissions at source.
-
Logistics and distribution: Modal shift, route optimisation, and carrier selection affect Categories 4 and 9.
-
Travel policy: Restricting non-essential flights and supporting active commuting options reduces Categories 6 and 7.
-
Science-based targets: SBTi's guidance on Scope 3 requires companies to cover at least 67% of total Scope 3 emissions in their targets if Scope 3 exceeds 40% of total emissions. For most companies, that threshold is crossed immediately.
The supplier engagement point is critical. Asking suppliers for emissions data without offering guidance, tools, or commercial incentives rarely works. The most effective programmes combine data requests with supplier support and link sustainability performance to procurement decisions over time.
Scope 3 reduction vs carbon credits: understanding the hierarchy
Carbon credits are not a substitute for Scope 3 measurement or reduction. That distinction matters, and any credible net-zero strategy depends on getting it right.
The correct sequence is:
-
Measure material Scope 3 categories
-
Reduce emissions through operational and supply chain action
-
Address residual emissions using high-quality carbon credits where reductions cannot yet be achieved
Carbon credits serve a legitimate role for residual emissions that remain after genuine reduction efforts. They do not offset the need to engage suppliers, redesign products, or shift procurement. Frameworks such as SBTi and the Oxford Principles on Net Zero Aligned Offsetting are explicit on this point: credits complement reduction, they do not replace it.
For companies building a net-zero strategy, the Scope 3 inventory is the foundation. It tells you where the emissions are, which reductions are feasible, and where a credible carbon credit strategy can play a supporting role.
What to do next
If your organisation is starting its Scope 3 journey, here are five concrete steps:
-
Read the full picture first. Understand how Scope 3 fits alongside Scope 1 and Scope 2 emissions before scoping your inventory.
-
Run a materiality screen. Map all 15 categories against your business model and identify the top 3-5 most likely to be significant.
-
Assign cross-functional ownership. Bring finance, procurement, operations, and HR into the process from the start.
-
Choose a proportionate data method. Start with spend-based estimates for material categories and build toward activity-based data over time.
-
Connect to your wider reporting obligations. Review your SECR reporting requirements and consider how Scope 3 data feeds into your broader net-zero commitments.
Use Thallo's free carbon footprint calculator to establish your Scope 1 and 2 baseline, then build your Scope 3 programme on top of it.
Frequently asked questions about Scope 3 emissions
What are Scope 3 emissions?
Scope 3 emissions are all indirect greenhouse gas emissions that occur in a company's value chain, excluding Scope 2. They cover both upstream activities (such as purchased goods and services) and downstream activities (such as the use of sold products). They are defined and categorised by the GHG Protocol into 15 distinct categories.
How do you calculate Scope 3 emissions?
Start with a materiality assessment to identify the most significant categories for your business. Then apply a proportionate calculation method: spend-based estimates using financial data are a valid starting point. More precise activity-based or supplier-specific data can be added over time as your programme matures.
Is Scope 3 reporting mandatory in the UK?
Not universally. SECR focuses primarily on Scope 1 and 2. However, UK SRS S2 (mandatory for listed companies from 2027) embeds Scope 3 on a comply-or-explain basis, and CSRD applies to companies above certain thresholds with EU exposure. Voluntary disclosure via CDP is also increasingly expected by investors and customers.
What are the most important Scope 3 categories?
It depends on your sector. Category 1 (purchased goods and services) is typically the largest for manufacturers and retailers. Category 11 (use of sold products) dominates for companies selling energy-consuming goods. Category 15 (investments) is critical for financial services. Categories 6 and 7 (business travel and employee commuting) are often most material for service businesses.
How do you reduce Scope 3 supply chain emissions?
Supplier engagement is the primary lever for most businesses. This means collecting supplier emissions data, setting procurement requirements, prioritising lower-carbon suppliers, and over time embedding emissions performance into supplier selection and contract terms. Science-based targets under SBTi provide a recognised framework for setting credible Scope 3 reduction goals.
