One box when you overpay your mortgage is worth €6,111

You have €10,000 saved and a €150,000 mortgage over thirty years at 3%. You have been paying €632.41 a month for five years and you still owe €133,359. You go into the branch, say you want to overpay, and they ask the usual question: shall we lower the monthly payment or shorten the term?

If you lower the payment, you start paying €584.98: €47.42 a month back in your pocket, and you finish on exactly the day you were always going to finish. You save €4,226 in interest.

If you shorten the term, you keep paying the same €632.41 and you finish 32 months early. Two years and eight months with no mortgage. You save €10,338.

Same money, same day, same desk. Between one box and the other there are €6,111, the price of a second-hand car.

It is not magic: by shortening the term you keep paying the old amount every month, and that extra slice goes entirely to capital. By lowering the payment you stretch out the time the capital takes to come down, and interest is charged on whatever is left.

If you say nothing, the contract usually applies the payment reduction by default, which is precisely the one that saves you least.

Ask for both simulations in writing, compare only the «total interest» line, and tick the box yourself.