The narrow definition of uncollectible receivables refers to those loans that do not generate revenue, and where it is impossible to expect full repayment of principal and interest in the future, as well as loans for which repayment of principal or interest is late for 90 days or more, or loans where the currency payment is due, but the charge is not made completely. The key problem that tends to show in this paper is the problem of non-performing loans, so in the first part of the paper, all factors that lead to this problem will be shown. The goal of this paper is to show how important it is for the stability of the banking system that the level of non-performing loans is as low as it can be . Regarding the second part of the work, the state of non-performing loans in Serbia will be shown, with emphasis on the situation in the EU and some countries in in the region. Followed by concluding observations.