In the article, the authors deal with the basic features of contracts on the provision of financial services. The definition of these contracts can be found in the relevant financial market regulation. According to that, financial services contract means a contract between a customer and a financial institution under which the financial institution provides the customer with a financial service (in particular a current account agreement, an insurance contract, a credit agreement, a securities purchase contract, a portfolio management contract, a participant agreement, an employer agreement, an old-age pension scheme agreement). One of the parties to these contracts is always the supervised entity on financial market. The authors focus their attention on those contracts whose subject matter is the custody of assets. Particular attention is paid to the institute of interest, which is associated with loan (credit) and deposit agreements. The article points out the basic principles of the legal regulation of these two contracts for the provision of financial services in the historical context, particularly in Roman law. In this context, it should be noted that interest was perceived controversially, especially in the Middle Ages, and was subject to a ban by Catholic Church. Furthermore, the subject of the article is a historical interpretation of the content of the fiduciary relationship, which the authors consider to be a key for the management of assets in the financial market. Thus, the classical fiducia did not represent the appreciation of the entrusted property, but the securing of the claim. In the second part of the paper, the subject of the analysis will be selected issues of regulation of some banking contracts and investment service contracts and the possibility of introducing negative interest rates on bank deposits.