When official emission factor databases (EPA, DEFRA, IPCC, regional sources like Brazil's PBGHG) release updated values, there is currently no way in Microsoft Sustainability Manager to track which version of a factor was used in a given calculation run, or to re-run historical periods with updated factors for comparison.

This is a growing compliance risk as regulations like CSRD and SEC climate disclosure rules require organizations to demonstrate methodological consistency over time.

We request the following improvements to the Emission Factors table and calculation engine:

1. Each emission factor should carry an effective date range and a source/version tag (e.g. "EPA 2024", "DEFRA v1.3")
2. Calculation profiles should lock to a specific factor version at run time, preserving a fully reproducible record
3. A "re-calculate with updated factors" option should allow users to compare prior-period results against newer factor versions without overwriting the original
4. An audit log should record which factor version was active at the time each calculation was executed

This would benefit any organization preparing for mandatory ESG disclosure, where auditors and regulators routinely ask which factor was used and why. It would also improve the calculation profile migration experience, as versioned configurations are significantly easier to move between environments.