What are carbon budgets?

In 2026, the UK set its seventh carbon budget, covering emissions up to 2042.

What are carbon budgets?

Carbon budgets set a legally binding cap on the maximum level of emissions (‘the net UK carbon account’) for a period of five years. In effect, a carbon budget is the amount of carbon that the UK has available to ‘spend’ in a set time frame, like a personal budget for shopping.

The government sets carbon budgets 12 years in advance through secondary legislation under the Climate Change Act 2008. The UK’s carbon budgets are being gradually reduced over time, with the aim of reaching ‘net zero’ carbon in 2050.

There have been seven carbon budgets set so far (covering 2008 to 2042). These budgets are set out in the table below.

Carbon budget Year Emissions Percentage reduction Has the budget been met? Carbon budget 1 (CB1) 2008 to 2012 3,018 million tonnes of carbon dioxide equivalent (MtCO2e) 26% reduction on 1990 levels 2,282 MtCO2e, equivalent to a 23.6% reduction on 1990 levels CB2 2013 to 2017 2,782 MtCO2e 32% reduction on 1990 levels 2,398 MtCO2e, equivalent to a 40% reduction on 1990 levels CB3 2018 to 2022 2,544 MtCO2e 38% reduction on 1990 levels 2,153 MtCO2e, equivalent to a 50% reduction on 1990 levels CB4 2023 to 2027 1,950 MtCO2e 52% reduction on 1990 levels The Climate Change Committee has assessed that the UK is on track to meet CB4 CB5 2028 to 2032 1,725 MtCO2e 58% reduction on 1990 levels CB6 2033 to 2037 965 MtCO2e 77% reduction on 1990 levels CB7 2037 to 2042 535 MtCO2e 87% reduction on 1990 levels What is the current carbon budget?

We are currently within the fourth carbon budget (CB4).

The UK has over-achieved emissions reductions across its first three carbon budgets, cutting emissions across multiple sectors to levels below the carbon budgets.

The independent Climate Change Committee has assessed that further action is needed to remain on track for the UK’s target of reaching net zero by 2050, but that emissions are well on track to achieve CB4 (2023 to 2027). The committee found that emissions reductions to date have largely come from the energy supply sector. It said that beyond CB4, more than three quarters of the required emissions reductions will need to come from other sectors, and that the government should focus on electrification to decarbonise multiple parts of the economy.

What changes do future carbon budgets contain?

The sixth carbon budget (CB6) was set in 2021, covering the period 2033 to 2037. Following advice from the Climate Change Committee, CB6 is the first carbon budget to include emissions targets for the international aviation and international shipping sectors.

As well as the carbon budgets, the UK has also made an international commitment through its ‘nationally determined contribution’ to the Paris Agreement, to reduce emissions by 81% from 1990 levels by 2035. The government has said that this target aligns with the ambition required to deliver CB6 (to reduce emissions by 77% from 1990 levels by 2037).

The seventh carbon budget (CB7) was set in June 2026. The Climate Change Committee published advice to the government on CB7 in February 2025, and supplementary cost analysis in March 2026. The government laid draft CB7 legislation before Parliament in June 2026, which was subject to affirmative procedure. This was debated and passed in both the Lords and the Commons. The level of CB7 was set at 535 MtCO2e, equivalent to a reduction of 87% on 1990 levels. As with CB7, it includes emissions from international aviation and international shipping.

CB7 set the government’s target for emissions reductions up to 2042: eight years before 2050, the year that the UK has committed to reaching net zero.

How is progress measured?

The government set out its approach to meeting the carbon budgets in its Carbon Budget Delivery Plan in March 2023, which was updated as the Carbon Budget Growth and Delivery Plan in October 2025. In setting CB7, the government committed to producing an updated delivery plan.

The Climate Change Committee is responsible for assessing progress against the carbon budget targets and publishes annual progress reports to Parliament. To date, the UK has met its first three carbon budgets and is on track to meet CB4.

For more information on this topic, see the Commons Library briefing on The UK’s plans and progress to reach net zero by 2050.