What is a carbon tax and how does it work?

Quick Answer: A carbon tax is a fee charged by a government on the greenhouse gas emissions produced by burning fossil fuels or other carbon-intensive activities. It works by putting a direct price on each tonne of CO2 (or CO2-equivalent) emitted, making higher-carbon choices more expensive and lower-carbon alternatives more competitive. Carbon taxes are one of the main policy tools governments use to reduce national emissions in line with climate targets.

What is a carbon tax?

A carbon tax is a price set by government on carbon dioxide emissions, typically expressed as a cost per tonne of CO2 or CO2-equivalent (CO2e). The logic is straightforward: when emitting carbon has a financial cost, businesses and individuals have an incentive to reduce it.

The tax is usually applied at the point of emission or at the point where the fuel enters the economy, such as when a company purchases fossil fuels or operates carbon-intensive processes. The cost then flows through the supply chain, making higher-emission goods and services more expensive relative to lower-emission alternatives.

Carbon taxes are distinct from carbon markets (such as emissions trading schemes), where companies buy and sell permits to emit. A carbon tax sets the price and lets the volume of emissions adjust. A carbon market sets the volume and lets the price adjust. Both are forms of carbon pricing, but they operate differently in practice.

How does a carbon tax work in practice?

Governments set a fixed rate per tonne of CO2e emitted. In the UK, the Carbon Price Support mechanism applies to fossil fuels used in power generation, sitting alongside the UK Emissions Trading Scheme (UK ETS). In other countries, such as Canada and Sweden, broader carbon taxes apply directly to fuel use across sectors.

The rate can be flat or escalating. Many carbon tax regimes include a pre-announced schedule of rate increases, giving businesses time to plan. Sweden's carbon tax, for example, started at around SEK 250 per tonne of CO2 in 1991 and has risen to over SEK 1,300 per tonne (roughly £95-100) by the mid-2020s, making it one of the highest rates in the world (World Bank, 2024).

Revenue raised from carbon taxes is handled differently depending on the government. It may be:

• Household rebates: Canada's federal carbon pricing system returns most revenue directly to households through quarterly payments, with lower-income households typically receiving more than they pay in higher fuel costs.
• Tax cuts: Revenue can reduce taxes on labour or corporate income, offsetting some of the drag on economic output.
• Clean energy investment: Governments can direct funds toward low-carbon infrastructure, technology development, or climate adaptation.
• Deficit reduction: Revenue can reduce public borrowing, though this approach does less to address the regressive nature of the tax.

How the revenue is used affects public and business acceptance of the tax, but does not change its core function of pricing emissions.

What is the difference between a carbon tax and an emissions trading scheme?

Both are carbon pricing mechanisms, but they work through different levers.

A carbon tax sets a fixed price per tonne of CO2e. Businesses know exactly what they will pay, which makes financial planning predictable. The trade-off is that the total volume of emissions is not capped, so the environmental outcome depends on how strongly the price signal changes behaviour.

An emissions trading scheme (ETS) sets a cap on total emissions and issues permits up to that cap. Companies that emit less can sell unused permits; those that emit more must buy additional ones. The total volume of emissions is controlled, but the price fluctuates with market demand.

In practice, many jurisdictions use both. The UK operates the UK ETS for large industrial emitters and power generators, while other carbon pricing mechanisms apply to sectors outside the scheme.

Why does a carbon tax matter for businesses?

For most businesses, a carbon tax affects costs indirectly through energy bills and supply chain prices rather than as a direct levy on the company itself. However, as carbon pricing regimes expand in scope and rate, direct exposure is increasing.

The EU's Carbon Border Adjustment Mechanism (CBAM) is a clear example of this shift. Introduced in 2026 (with a transitional reporting phase from 2023), CBAM requires importers of certain carbon-intensive goods into the EU to pay a carbon price equivalent to what would have been paid under the EU ETS if the goods had been produced in Europe. This means that UK and non-EU businesses exporting to Europe now face direct carbon pricing exposure, even if they operate outside a domestic carbon tax regime.

For businesses subject to supply chain due diligence, procurement requirements, or customer sustainability questionnaires, understanding your own carbon footprint is increasingly a prerequisite for demonstrating compliance. Schemes like PPN 006 (for UK public sector suppliers) and frameworks like EcoVadis already require carbon data. As carbon pricing spreads, having an accurate, auditable emissions inventory becomes relevant to commercial risk, not just reporting.

This is where tools like Seedling become practically useful. Knowing your Scope 1, 2, and 3 emissions gives you the foundation to assess your exposure to carbon pricing, identify where your highest-cost risks sit, and make informed decisions about reduction priorities.

What are the arguments for and against carbon taxes?

Carbon taxes are well-supported in economic theory but contested in practice. The main arguments on each side are worth understanding clearly.

Arguments in favour:

• They put a direct price on pollution. By attaching a cost to each tonne of CO2 emitted, a carbon tax changes the economics of high-emission choices without the government having to dictate how businesses reduce. The market works out the most efficient route to cuts.
• They give businesses certainty. Unlike an emissions trading scheme, where permit prices fluctuate with market demand, a carbon tax sets a known rate in advance. 
• Revenue can be put to productive use. The funds raised can be recycled through household rebates, reductions in other taxes, or investment in clean infrastructure. 
• They are relatively straightforward to administer. Carbon taxes can be applied at the point of fuel purchase or energy use, using existing tax collection infrastructure. That makes them easier to implement and enforce than permit-based systems, particularly for smaller emitters.

Arguments against:

• They can be regressive. Higher energy and fuel costs hit lower-income households harder, because energy makes up a larger share of their expenditure. Without careful revenue recycling, a carbon tax can shift the burden onto those least able to absorb it.
• They risk carbon leakage. If domestic producers face a carbon cost that competitors abroad do not, emissions may not fall overall; production simply moves to jurisdictions with weaker rules.
• The right rate is genuinely difficult to set. Too low, and the price signal is too weak to change behaviour. Too high, and the economic disruption may outpace the capacity of businesses and households to adjust. 
• They are politically exposed. Carbon taxes are visible and attributable in a way that makes them a target for opposition, particularly when fuel prices are already high.

The carbon leakage problem is one reason mechanisms like CBAM exist: to level the playing field for domestic producers and prevent emissions from simply moving across borders.

How carbon taxes connect to your emissions data

A carbon tax creates a financial consequence tied directly to emissions volume. The higher your emissions, the greater your exposure, whether through direct taxation, energy costs, or supply chain pricing pressure.

Accurate carbon accounting is the starting point for managing that exposure. Without a reliable picture of where your emissions sit across Scopes 1, 2, and 3, you cannot identify which parts of your operations carry the most financial risk under current or future carbon pricing, nor can you model the impact of reduction initiatives with any confidence.

As carbon tax rates rise and carbon border mechanisms expand, the gap between businesses with good emissions data and those without will become increasingly visible in commercial terms, not just in sustainability reports.