Fiscal neutrality and proportionality are the most crucial core features in the VAT system. The ECJ has reconfirmed this in a recent court case, C-717/19, by its rationale in the final judgment by confirming that “the amount collected by the tax authorities must not exceed the amount paid by the final consumer, i.e., member states are obliged to reduce the taxable amount in all cases where the taxable person does not receive the whole or part of the consideration after the transaction has been completed”.
Source PwC
See also