France: the TVA is inside the price, the malus may not be
TVA at 20% is already inside the advertised price, so a French car loan has no purchase tax to add and the field is absent on this page. Registration and first-year charges are small against the price of the car.
The exception is the one figure worth checking before you trust the payment. The CO2 malus can add several thousand euros on a high-emission car, and it is not modelled here, because it depends on the vehicle's emissions rather than on any percentage of its price. If the quote you are working from is a price before the malus, add the malus amount to the fees field; it is normally financed with the car, so putting it there rather than treating it as cash gives the honest monthly figure.
Because there is no itemised purchase tax, a trade-in in France reduces the amount financed by its equity and nothing else, there is no tax credit of the kind an American part-exchange earns.