The article presents the methodology of comparing loans in line with the European Union recommendations. The measure used to compare loan offers is APR (annual percentage rate), calculated according to the formula of internal rate of return and considering, apart from interest cost, also other costs to be borne by the borrower to obtain a loan. It is important since existing legislation does require banks to apply uniform measures to determine loan price. It is obvious, therefore, that banks use interest calculation methods, repayment schedules and different fees and charges that increase loan price. As a consequence, we have non-transparent market and inability to compare offers of different banks without adequate calculations.

The second topic of the article is, established by the authors, a simplified methodology of APR calculation. The method is not detailed enough to be used as an equivalent of the detailed linear interpolation method. The authors worked out a matrix of approximate increase values of the periodic interest rate on a loan Dj (%) resulting from one percentage point change of the fee p for a given number of installments n, and nominal interest rate on an annual basis.

The third part is devoted to the analysis of 10 credit offers obtained from Warsaw branches of Polish banks. For each offer the repayment schedule was determined. In case the schedule was different from any known and commonly applied debt repayment schedules the authors prepared the repayment algorithm. Then, APR was calculated for all offers, and most attractive loan was selected. It was found out that the loan with one of highest interest rates was cheapest.

Moreover, the analysis proved that Polish banks often use repayment schedules that breach financial mathematics rules. The authors also learnt to their surprise that with h installment, calculated by one the banks under analysis, the customer paid interest calculated at the end-period for the previous month and in advance for the repayment day (this refers to the loan repaid in descending installments). Additionally, the bank assumes that all months have 30 days, except for the first one that is one day longer - which is against the rule of time calculus.