Thresholds move every 1 July — why a classification goes stale

The CO2 emission class is not a property of the vehicle. It is the ratio between the vehicle's specific emissions value and a reference value — and that threshold keeps moving.

The mechanism

Each vehicle sub-group has a reference value, and the thresholds for classes 2, 3 and 4 are derived from it. Those thresholds tighten every year along a trajectory fixed in advance.

The detail easiest to miss is the most important one: the period runs from 1 July to 30 June of the following year, not by calendar year. A journey on 30 June still falls under the old thresholds; on 1 July it is under the new ones.

What that means in practice

The vehicle has not changed. Its emissions value is the same. But the threshold has moved, and it may no longer fall in the same class.

In Germany the class itself is re-determined every six years

Two different things get confused here. Thresholds move annually — that is the general rule. But the assignment to classes 2 and 3 in Germany is re-determined every six years, counted from that vehicle's first registration date, against the thresholds in force on the review date.

That yields something useful for planning: every vehicle has its own date. It is not a shared annual deadline but a date you can calculate in advance from the registration certificate.

Legal basis: BFStrMG Annex 1 point 4, as in force from 1 December 2025.

Two directions, two different risks

Stale against you. Class one declared although the vehicle qualifies for class three. You overpay, and the overpayment can be recovered.

Stale in your favour. Class three declared although under current thresholds the vehicle falls in class two. You are being charged too little.

The second case is not a win. An incorrect declaration is the declarant's responsibility, and the difference may have to be paid back. An audit that checks only one direction is unfinished — and we report the second direction as a warning, never as your benefit.

When to check

Once a year, after 1 July, when the new thresholds take effect. And every time a vehicle joins the fleet — because it lands in class one by default until the documents are filed.

What must not be done

Guessing. Classification rests on the specific emissions value from the certificate of conformity or the manufacturer's data. Without it the class cannot be determined, and a guess leads either to an unfounded claim or to an incorrect declaration. Where that value is missing, our system does not compute a class and does not raise a finding.