It’s the same in Germany, it’s laid out in the mortgage terms. As a rule of thumb, you can pay up to 5% of the principal in a single lump sum every year on top

It’s the same in Germany, it’s laid out in the mortgage terms. As a rule of thumb, you can pay up to 5% of the principal in a single lump sum every year on top of your usual payments directly reduces the principal at no extra fee. You can negotiate higher yearly extra payments, but that usually comes at the cost of higher interest. Sometimes you’re able to refinance at no prepayment fee, but that comes down to how hard the bank wants to keep you as a customer etc.