# How long is a product carbon footprint valid before my buyer needs a new one?

Canonical: https://senseible.earth/answers/pact-pcf-validity-three-years

Up to three years under PACT Methodology v3.0, as long as nothing major changes. A change of 10% or more against the original footprint ends it early, and you recalculate and resend. Validity starts after the footprint's reference period, and your buyer can only use it if it is valid within the reference period of the buyer's own footprint.

## The rule

- Maximum validity: up to three years, provided the production process has no major change in that time.
- Major change: a variance of 10% or more compared with the original footprint.
- After three years, or once such a variance is found, the footprint is no longer representative and must be recalculated and exchanged again.
- You may update more often, for example every year.

## When the clock starts

Validity starts automatically after the reference period, unless you specify otherwise. The reference period runs from the start of the earliest activity data used to the end of the latest, and it must always be disclosed. You may average over several years to smooth out shutdowns or unusual production.

## What your buyer checks

A buyer may only use your footprint if its validity period falls within the reference period of the footprint the buyer is calculating. The buyer's own footprint is not cut short when yours expires, but its next calculation will need a valid figure from you.

## What usually triggers a recalculation

- A new main raw material or main supplier.
- A fuel switch, for example furnace oil to gas or biomass.
- Rooftop solar or a green power contract that changes your electricity figure.
- A process change that moves yield or scrap rates.
- Run the 10% test on each: estimate the new figure and compare it with the one your buyer holds.

## Example: a footprint for FY 2025-26

- Reference period: 1 April 2025 to 31 March 2026
- Valid from 1 April 2026 for up to three years, to 31 March 2029
- Original footprint 2,800 kg CO2e per tonne; rooftop solar in 2027 brings it to 2,500
- Variance: 300 / 2,800 = 10.7%, so recalculate and resend now

Footprint values are example figures.

## What Senseible does here

Senseible keeps your fuel and electricity records month by month from your bills, so when a change may cross 10%, the new energy figures are already there to recalculate with. It does not send data in the PACT format.

- [Supplier evidence for buyers](https://senseible.earth/scope-3-supplier-evidence)
- [How often to update figures for a buyer](https://senseible.earth/answers/how-often-update-emissions-data-for-buyer)
- [What a PACT verifier checks](https://senseible.earth/answers/pact-pcf-verification-what-gets-checked)

Sources: [PACT Methodology v3.0, section 3.2.3 (Partnership for Carbon Transparency)](https://docs.carbon-transparency.org/tr/methodology/3.0/pact-methodology-v3.0.pdf)

Last reviewed 2026-11-03. Check the current PACT Methodology version for changes to validity periods.