Irish Car Tax Bands Explained: CO2, Engine Size and What They Mean

Irish car tax — officially called “motor tax,” the term you’ll see on the bill and on motortax.ie — has used three completely different ways of calculating what you owe, and which one applies to your car depends only on when it was first registered — not on its CO2 emissions alone.

The three systems

Registered before 1 July 2008: engine size (cc). Nothing to do with emissions. A bigger engine costs more, in cc bands from “up to 1,000cc” up to “3,001cc and over.”

Registered 1 July 2008 to 31 December 2020: NEDC CO2 bands. Twelve bands, A0 (0g/km) through G (226g/km and over), based on the old NEDC lab test. Rates run from €120 a year at the bottom to €2,400 at the top.

Registered from 1 January 2021: WLTP CO2 bands. The EU moved to a stricter, more realistic lab test (WLTP) in 2021, which generally reports higher CO2 figures than NEDC did for the same car. To avoid pushing everyone into a worse band just because the test changed, the WLTP table has more, narrower bands — sixteen instead of twelve — and different g/km thresholds for each one.

This is the part that catches people out: two cars with the same CO2 figure on paper can be taxed completely differently if one was tested under NEDC and the other under WLTP. You can’t look up a CO2 number against a single table — you need to know which test regime applies first, and that depends on the registration date, not the number itself.

Why this matters for reading fleet statistics

CSO’s own vehicle fleet data (which the county pages on this site are built from) records each car’s CO2 band using labels like “Band A1” or “Band C1” — but doesn’t separately record which test regime assigned that label. A car in “Band A1” could be an NEDC-era car taxed at a different rate than a WLTP-era car also sitting in a band called “A1”. That’s a real, documented limitation: it means a county’s most common CO2 band, which you’ll see noted on each county page, tells you about the shape of the fleet, but it is not enough on its own to calculate the average tax bill in that county — doing that correctly would require knowing each vehicle’s registration date alongside its band, which this dataset doesn’t expose together.

Work out your own band

Use the car tax calculator: pick your registration period, enter your engine size or CO2 figure, and it looks up the exact band and annual rate from the official tables.