The government estimates the reimbursements could total 40-50 million euros.
The Court agreed with the European Commission that Finland's taxation policy discriminates against individuals who bring in second-hand vehicles from other EU countries.
Individuals who bought used cars abroad were subject to Finnish car taxes, and then paid an additional sales tax. Companies, on the other hand, were allowed to deduct the Finnish sales tax they paid on the vehicle if they sold it on to a private owner.
It is this special favour to companies that was challenged in court.
The ruling affects around 170,000 vehicles that have been brought into Finland since 2006. The decision will not affect future personal car imports, as new legislation on the matter takes effect next month.