You can deduct half of VAT for passenger cars, the rest becomes a deduction from income tax. The invoice for 100 PLN includes 18 PLN VAT, we have 9 PLN for the deduction. The rest – PLN 91 is deducted from income tax. For rental contracts, the rate is 8.5%, so if there would be no refund – the rental amount would be PLN 91 higher, i.e. you would have to pay tax by PLN 7.7 more. Hence, the total invoice profit is PLN 9 VAT + PLN 7.7 (income tax). = PLN 16.7. In summary – by collecting invoices – you recover 17% of the amount spent.