The Carbon Reduction Commitment's 90 percent emissions rule, otherwse known as the 'flexible de minimis' rule, requires all particpants to account for at least 90% of their total carbon footprint emissions. The 90% rule aims to focus attention on the largest, and most cost effective, opportunities to reduce carbon emissions.

The 90% emissions rule can include all energy reported through the Climate Change Agreement, European Union Emissions Trading Scheme, as well as all 'Core Sources' of non-transport energy consumption.

In particular circumstances, some organisations in the UK will not be affected by the carbon reduction commitment. Where an organisation already has 90% of its emissions covered by the EU Emissions Trading Scheme or the Climate Change Agreement, it may be exempt from being included in the carbon reduction commitment.

Direct emissions covered by the European Union's emissions trading scheme are exempt.

Under the climate change agreement, a subsidiary will be exempt if more than 25% of the total energy is covered by the CCA.