The concrete amount is individual to each case, of course. It depends on the penalty terms agreed upon in the mortgage contract. Sometimes it is a fixed amount (an equivalent of six months of interest, for instance), or a percentage of the outstanding balance, fixed (around 2%) or regressive. For example, the penalty for prepaying the mortgage in its first year may be 5% of the original balance, in the second year – 4%, in the third year – 3% etc.