PCF Reporting Periods Explained: How to Align Factory, Supplier, and Emission Data

A practical guide to using data from different years without weakening your product carbon footprint

Short answer: A Product Carbon Footprint does not always require every input to come from the same year. However, the calculation must represent a clearly defined production period, and any differences between factory data, supplier data, emission datasets, and BOM versions should be assessed and documented.

A PCF is calculated at a specific point in time, but the information used in the calculation may come from different periods.

For example:

• Factory electricity data: 2025
• Supplier PCF: 2024
• Emission dataset: 2023
• BOM revision: updated in March 2025
• Customer request: “Provide the 2025 product carbon footprint”

This situation is common. It does not automatically make the PCF invalid. The important question is whether the data remains representative of the product, production process, suppliers, and period being assessed.

What is a PCF reporting period?

The reporting period is the time period that the PCF is intended to represent.

For a manufactured product, it may be:

• A calendar year
• A financial year
• A production campaign
• A defined batch
• A season
• A period covering a specific product revision
• A representative period for a new or low-volume product

The reporting period should not be confused with:

• The date the calculation was completed
• The publication date of the report
• The year in which an emission dataset was released
• The date on a supplier certificate

A PCF completed in 2026 may represent production during 2025. Its secondary datasets may have been published in 2024 or earlier.

The report should state these dates separately.

Does every PCF input need to come from the same year?

Usually, no.

Using one consistent reporting year is preferable when suitable data is available, but real supply chains rarely provide every input from exactly the same period.

Different data years may be acceptable when:

• The product and process have not materially changed
• The supplier and production site remain representative
• The older data is still the best available source
• The difference in year is assessed and documented
• The data is not presented as more current than it really is

The key principle is:

Data should represent the product and process being assessed, not simply match a calendar year on paper.

A 2024 supplier PCF may be more representative of a 2025 product than a generic 2025 dataset if the supplier, material, production route, and site are unchanged.

However, older data should be reviewed rather than accepted automatically.

Reporting period, reference year, and publication date

These three dates are often confused.

Reporting period

The period represented by the activity data.

Example: factory electricity and production volume from January to December 2025.

Reference year

The year associated with a dataset or emission factor.

Example: a 2023 database value for aluminium production.

Publication date

The date on which a report, dataset, or supplier declaration was issued.

Example: a supplier PCF published in June 2024.

A report should identify all three where relevant.

For example:

This PCF represents Product A manufactured at Site B during calendar year 2025. Supplier-specific data represents 2024 production. Secondary datasets are from database version 2023. The data was reviewed for technological and geographical relevance.

How to handle data from different years

When factory, supplier, and secondary data come from different periods, review the difference systematically.

Ask:

1. Has the product changed?
2. Has the BOM changed?
3. Has the supplier or production site changed?
4. Has the manufacturing process changed?
5. Has the electricity or fuel source changed?
6. Has the recycled content changed?
7. Has the transport route changed?
8. Could the difference materially affect the PCF?

If the answer to the final question is no, the older data may remain suitable with a documented explanation.

If the answer is yes, update the input, calculate a scenario, or disclose the uncertainty.

Factory data from a different year

Factory energy and production data should normally represent the period in which the product was manufactured.

For example, if the PCF represents 2025 production, use 2025 data where possible:

• Electricity
• Natural gas
• Steam
• Fuel
• Production volume
• Scrap and yield
• Process emissions
• Packaging production

If 2025 data is unavailable, possible alternatives include:

• The nearest complete year
• A representative production campaign
• A production-weighted average
• A documented estimate based on available months

Do not use an abnormal period without explanation.

For example, a factory may have experienced:

• A long shutdown
• Unusually low production
• Temporary use of backup generators
• Major equipment replacement
• A change in electricity contract
• A production transfer to another site

In these situations, the reporting period may not represent normal production. The report should explain whether the data was used as recorded, adjusted, or supplemented with another period.

Supplier PCF from an older year

An older supplier PCF may still be useful if the underlying conditions remain substantially the same.

Before using it, check:

• Same supplier
• Same production site
• Same material or component
• Same grade or specification
• Same production route
• Similar recycled content
• Similar energy source
• Same declared unit
• Comparable included stages
• No significant process change

For example, a supplier PCF from 2024 may be used in a PCF representing 2025 production if:

• The material grade is unchanged
• Production remains at the same site
• The supplier confirms that the process has not materially changed
• The recycled-content claim remains valid
• The calculation scope is compatible

The report should still state that the supplier data represents 2024 rather than 2025.

Suitable wording:

The supplier-specific PCF represents production during 2024. The supplier confirmed that the production site, material grade, production route, and recycled-content percentage remained unchanged during the 2025 reporting period.

If the supplier changed its process, site, electricity source, or material composition, the older PCF may no longer be representative.

Older emission datasets

Emission datasets often have a reference year that differs from the PCF reporting period.

This does not automatically make them unusable. The dataset should be assessed for:

• Material and process match
• Geography
• Technology
• Reference year
• Database version
• Included life-cycle stages
• Treatment of recycled content
• Electricity assumptions
• Data-quality indicators

A 2023 dataset may be acceptable for a 2025 PCF if it remains the best representative source and no significant technological or geographical change is known.

However, avoid using old data without explanation, especially for:

• Electricity-intensive materials
• Fast-changing energy systems
• Materials with rapidly changing recycled content
• New manufacturing technologies
• Regions undergoing major grid changes
• Supplier processes affected by regulation or fuel switching

The report should record the dataset’s reference year and explain why it was selected.

What if the BOM changed during the year?

A BOM revision is one of the most important PCF dates.

If the product changed during the reporting period, first determine whether the change affects:

• Material type
• Material quantity
• Product weight
• Supplier
• Recycled content
• Manufacturing process
• Packaging
• Product performance
• Expected use or lifetime

A minor change may have no material effect. A change from virgin to recycled material, or from aluminium to plastic, may significantly affect the result.

Possible approaches include:

Calculate each revision separately

Use this when the revisions are materially different or sold as distinct products.

Use the current revision only

Use this when the customer requests the current product and earlier revisions are no longer relevant.

Calculate a production-weighted result

Use this when several revisions were produced and sold during the same period.

For example:

• Revision A: 60% of 2025 production
• Revision B: 40% of 2025 production

The report should identify both revisions and explain the weighting method.

Do not combine BOM revisions silently. A PCF must be traceable to a defined product configuration.

Seasonal products and campaign production

Some products are manufactured only during a specific season or campaign.

Examples include:

• Seasonal apparel collections
• Agricultural products
• Holiday packaging
• Construction materials produced for a specific project
• Products made during a limited production run

In these cases, a full calendar year may not be the most representative period.

A campaign or seasonal period may be more appropriate if it captures:

• The actual product materials
• The relevant production site
• The production technology
• The energy used
• The actual production volume
• Relevant packaging and logistics

The report should explain why the selected period represents the product better than an annual average.

For example:

The PCF represents the Spring 2025 production campaign because the product was manufactured only during that campaign. Annual factory data was used only to support the allocation of shared site energy.

New products and limited production data

New products may not have a full year of production data.

Possible approaches include:

• Using pilot production data
• Using a representative production batch
• Scaling measured data carefully
• Using a similar existing product as a temporary proxy
• Separating prototype and commercial production
• Clearly labelling the result as an estimate

A new product should not be presented as having a “2025 annual footprint” if it was produced only during a short pilot run.

Suitable wording:

This preliminary PCF represents the pilot production batch manufactured in September 2025. Commercial-scale production data was not yet available. Energy and yield assumptions will be reviewed after the first full production period.

Abnormal production years

A reporting year may contain unusual conditions that distort the result.

Examples include:

• Very low production volume
• Temporary shutdowns
• Major process trials
• Emergency fuel use
• Severe scrap events
• A temporary production transfer
• Unusual maintenance activity
• A new factory ramp-up period

Low production can make emissions per product appear unusually high because fixed energy is divided across fewer products.

Do not automatically remove abnormal data. First decide whether the PCF is intended to represent:

• Actual production during that period
• Normal operating conditions
• A typical future product
• A specific customer order
• A product sold during the reporting year

The chosen approach must be stated clearly.

How to align mixed-year data

The following table provides a practical approach.

When should a PCF be recalculated?

A PCF should be reviewed when important conditions change.

Recalculation may be appropriate when there is a material change in:

• BOM or product design
• Material quantity or grade
• Recycled content
• Supplier or production site
• Manufacturing process
• Electricity or fuel source
• Production yield or scrap
• Packaging
• Transport route
• Product use assumptions
• Applicable calculation rules
• Customer reporting requirements

An annual review is often practical, but an annual schedule alone is not enough. A major product or process change may require an earlier update.

The organisation should define what counts as a material change. This threshold may be quantitative, qualitative, or both.

For example:

Recalculate when a design or process change is expected to alter the product result materially, or when a customer, programme, or applicable rule requires an updated result.

How to disclose mixed-year data

A professional PCF should include a data-period register.

The report should also identify:

• Why different periods were necessary
• Whether the data represents actual or estimated conditions
• Which inputs are most sensitive to age
• Whether scenario analysis was performed
• Which data should be improved next

Suitable wording:

The PCF represents production during calendar year 2025. Factory and packaging data are from 2025. Supplier-specific data represents 2024 production and was retained because the supplier confirmed no material change in site, process, material grade, or recycled content. Secondary datasets are identified by reference year and version in the data register.

Common reporting-period mistakes

Avoid these practices:

• Treating the calculation year as the reporting period
• Presenting older supplier data as current-year data
• Omitting the reference year of emission datasets
• Combining BOM revisions without explanation
• Using a shutdown year as a normal baseline
• Ignoring supplier or process changes
• Updating the report date without updating the data
• Mixing data periods without assessing materiality
• Assuming newer data is automatically more representative
• Giving a precise result without explaining mixed-year inputs

Reporting-period checklist

Before publishing or submitting a PCF, confirm that the report identifies:

• Product model and BOM revision
• Declared or functional unit
• Production site
• Reporting period
• Factory activity-data period
• Supplier-data periods
• Secondary-data reference years
• Dataset versions
• Included life-cycle stages
• Significant changes during the period
• Treatment of seasonal or abnormal production
• Allocation and weighting methods
• Assumptions and estimates
• Recalculation triggers
• Review or verification status

Frequently asked questions

Does a PCF need to use one calendar year?

No. A calendar year is common, but a campaign, batch, season, or other representative period may be more appropriate. The selected period must be clearly defined and justified.

Can supplier data from a different year be used?

Yes, when it remains representative of the material, production site, process, and other relevant conditions. The supplier-data year must be disclosed.

How old can an emission dataset be?

There is no universal age limit that applies to every PCF. Assess the dataset’s material, technology, geography, reference year, and relevance to the intended use.

Can I use a 2024 supplier PCF for a 2025 product?

Potentially. Confirm that the product, site, process, material grade, recycled content, and included stages remain comparable.

What should I do if the BOM changed during the year?

Calculate each material revision separately or use a documented production-weighted result. Do not combine revisions without explanation.

Should abnormal production data be removed?

Not automatically. Decide whether the PCF should represent actual production or normal operating conditions, then explain the treatment.

When should a PCF be updated?

Review it annually or when a material change occurs in the product, supplier, site, process, energy source, recycled content, packaging, transport, or applicable requirements.

Conclusion

A strong PCF is not created by forcing every input into the same calendar year.

It is created by defining what period the result represents, checking whether each input is still representative, documenting differences between data periods, and updating important information when conditions change.

A trustworthy report should make clear:

• What production period was assessed
• Which data came from that period
• Which supplier and secondary data came from earlier periods
• Why those inputs were considered suitable
• Which assumptions could affect the result
• When the PCF should be recalculated

Mixed-year data can be acceptable. Hidden mixed-year data is the problem.

If your organisation needs a more structured way to document PCF data quality, reporting periods, and supporting evidence, Climate Seal can provide a practical next step. Explore Climate Seal and see how it can support more transparent, credible product carbon footprint reporting.

References and further reading

• ISO 14067:2018 — Greenhouse gases: Carbon footprint of products
• GHG Protocol Product Life Cycle Accounting and Reporting Standard
• GHG Protocol Scope 3 Calculation Guidance
• European Commission Environmental Footprint Methods