Should I include company vehicles in the CO2 emissions statement

Vehicle fleet is divided into two scopes, not one

Yes, the vehicle fleet must be included, but not as a single item. Own vehicles on own fuel — company cars that run on diesel or petrol — fall under scope 1: direct emissions. If the vehicle fleet runs electrically, that emission shifts to scope 2, because the emissions then occur during energy generation and not at the vehicle itself. Leased cars are the exception often overlooked: depending on the lease contract (operating or financial), the GHG Protocol requires them to be placed sometimes in scope 1 and sometimes in scope 3. If in doubt about what your customer means precisely by scope 1, that is detailed on the page on direct greenhouse gas emissions.

Those without fuel data per vehicle often use the total litres fuelled from invoices, or the mileage as an approximation. That is an accepted method, not a shortcoming — as long as the assumption is visible with the answer. If both fuel data and mileage records are missing, then "no, not yet calculated" is the honest answer; entering an estimate without underlying figures is riskier than leaving a field blank. Commuting of employees in their own cars is a different matter: that belongs in scope 3, not with the company vehicle fleet, and is explained on the page on emissions in the value chain.

Basis in the VSME module and the scope classification of the GHG Protocol

The VSME basic module of EFRAG requires emissions broken down by scope 1 and scope 2, and the GHG Protocol determines which source falls into which scope — fuel consumption of own or leased vehicles is a classic scope 1 example in that, unless the vehicle runs on purchased electricity. For the precise boundary between scope 1, 2 and 3 for mixed vehicle fleets (own, lease, electric) there is a detailed overview on the page on scope 1, 2 and 3 together.