Introduce GBP 120 carbon tax: note

Central fiscal result

-GBP 40.0bn - Net fiscal impact in 2028-29

Low case: -GBP 90.0bn. High case: -GBP 10.0bn. Positive numbers are fiscal costs or borrowing pressure. Negative numbers are Exchequer savings or receipts.

Scenario and baseline

• Models introduce gbp 120 carbon tax by 2028-29.
• Baseline is current policy or published departmental plans.
• Central case uses published party or official anchors where available.
• Wider manifesto interactions are excluded unless stated.

Affected population

• Affected units are people, firms, households or providers depending on policy.
• Direct exposure follows the manifesto or government target group.
• Indirect exposure includes suppliers, workers, consumers and taxpayers.
• Weakest counts are widened in the low and high cases.

Gross impact

• Published anchor or scenario central is +GBP 40.0bn in 2028-29.
• Gross costs or receipts are adjusted for behaviour and delivery risk.
• Tax, benefit or procurement offsets are separated in the fiscal build-up.
• The range is deliberately wider where implementation detail is thin.

Fiscal build-up, central case

• Gross tax or receipt yield: -GBP 50.0bn
• Behavioural and avoidance response: +GBP 8.0bn
• Administration and compliance cost: +GBP 0.1bn
• Other tax-base interactions: +GBP 1.9bn

Central net impact: -GBP 40.0bn in 2028-29.

Behaviour and pass-through

• Low case assumes stronger delivery or receipts than central.
• Central case applies moderate behavioural leakage and pass-through.
• High case allows weaker delivery, larger take-up or higher costs.
• Output effects follow incidence, capacity and investment channels.
• Distributional gains do not automatically imply GDP gains.

Phasing

• 2026-27: -GBP 4.0bn. Phased implementation and take-up.
• 2027-28: -GBP 22.0bn. Phased implementation and take-up.
• 2028-29: -GBP 40.0bn. Phased implementation and take-up.
• 2029-30: -GBP 40.0bn. Phased implementation and take-up.

Main source groups

• S1: Green manifesto and current party material define the scenario, not an official costing.
• S2: Official statistics and departmental baselines anchor affected populations and public spending.
• S3: Academic evidence informs behavioural, price, labour-supply and investment assumptions.
• S4: IFS and OBR-style reasoning support wide ranges where delivery or tax yields are uncertain.