Objectives:
The subject of the study is the Roman institution of pollicitatio, which is currently unknown. At most, it can be compared to a modern public promise. The institution of pollicitatio appeared in the municipal law and it was a public promise to build a public facility or organize a public event. Such a promise was most often made in connection with running for public office in order to gain the favor of voters. Roman lawyers were already wondering about the nature of this institution and the legal consequences it gave rise to. The institution of pollicitatio was a great support for city budgets, which at that time had full independence from central finance.

Material and methods:
The work collects and thoroughly analyzes the most important sources concerning the institution of pollicitatio. The aim of the conducted research is to analyze the political and economic context of the functioning of this sui generi public law institution.

Results:
As a research hypothesis, a thesis was put forward, according to which the municipalities of ancient Rome found a way to implement a solution in order to find finances for the implementation of public utility goals.

Conclusions:
The final conclusions stated that the nature of this institution should be clarified by referring it to institutions similar at that time, namely to promissio, donatio, votum or legatum. From the analysis of the sources of Roman law and the comparison of pollicitatio to other similar institutions existing at that time, it can be concluded that it was a unilateral promise to build a public facility or organize a public event by a private person, most often in connection with running for public office.