Compound interest is the only interest rate used in serious finances. It allows to compare products and to create competition. However, public mortgage quotas are calculated using an approximated formula (a mix between compound and simple interest). Apart from creating confusion, this makes mortgage interest rates to grow even greater when interest rates rise (as the approximation error gets larger).  In the old times, using the exact formula could be complex but, nowadays, even the phone on our pocket can calculate it. There is no excuse to continue using the approximated formula.  Please, change the law to force the use of the formula applying the effective annual interest rate (the universal interest rate unit).