The United Kingdom Emissions Trading Scheme (the “UK ETS”) was established by the Greenhouse Gas Emissions Trading Scheme Order 2020 (the “UK ETS Order”). The UK ETS runs for ten “scheme years” beginning in 2021. Operators of certain industrial installations and certain aircraft operators are required to monitor, report on, and surrender “allowances” equivalent to, their greenhouse gas emissions in each scheme year. Some operators and aircraft operators receive an allocation of allowances free of charge, details of which are published in allocation tables. Allowances are held in accounts in the UK ETS registry, and there is a cap on the number of allowances that may be created. For installations that meet the eligibility criteria, there are two opt-out schemes, one for “hospital or small emitters”, the other for “ultra-small emitters”. Such installations are not required to surrender allowances.