Some 69 companies listed on the FTSE 100 index – over two thirds – made prior-year adjustments on their climate and sustainability metrics in 2025, up from 46 the previous year, new data from Deloitte UK has revealed.
The number of companies disclosing multiple prior-year adjustments tripled year-on-year, to 51, from 17 in 2024.
Revisions resulting from reporting errors declined to 20% of all adjustments, from 26% a year earlier.
‘A core feature’
With adjustments increasing for the third year in a row, this recent data shows us they have become a core feature of FTSE 100 climate reporting,” commented Steve Farrell, partner and head of sustainability assurance at Deloitte UK.
“The decrease in error-driven misstatements indicates improvement in reporting quality, particularly as restatements due to changes in methodology, business structure and other factors, have increased significantly. This suggests a positive step from UK companies towards refining reporting processes and data quality, rather than merely correcting mistakes.”
Deloitte’s analysis, now in its third year, examined climate and sustainability reporting published by FTSE 100 companies in the period to 31 December 2025.
Greenhouse gas emissions accounted for the majority (65%) of prior-year adjustments, with the remaining 35% relating to topics such as waste, water, diversity and inclusion, and health and safety.
Improved accuracy
“The high volume of restatements indicates that companies are actively working to improve the accuracy and reliability of their Scope 3 reporting,” Farrell added. “It underscores the inherent challenges and complexities associated with collecting, calculating and assuring the data.”
Deloitte’s data also indicated that 86 FTSE 100 companies obtained external assurance for sustainability metrics in 2025, compared with 84 the previous year and 74 in 2023. ISAE 3000 remained the most widely used framework, with four fifths (79%) of assurance engagements providing either limited or reasonable assurance under the standard. Read more here.
