The article presents relations between a bank and economic subject as generated by civil law contracts. Characteristic features of such relations have been discussed more largely on account of two particular groups of contracts: - contracts with bank as a debtor of a firm, - contracts with bank as a creditor o f a firm. The analysis of relations happening between the two parts of a contract is being done in aspect of credibility of economic subject itself. Taking the last in consideration a bank proceeds to a segmentation of the portefeuille of its clients. This is obligatory in case of clients that have some obligations towards the bank - a subject is being classified to a group in conformity with evaluated risk o f a transaction....