The author has outlined the essence of legal presumptions on discretion in law enforcement of financial legal provisions as both current legal phenomena and legal regulations. The relationship between presumptions and principles of law, as well as the classification of presumptions has been researched into. Presumptions on discretion in law enforcement of financial legal provisions are formed in relation to a particular legal fact or group of facts or compositions that correspond with a particular law enforcement situation, which is due to the origin, content and purpose of these facts or compositions, the relationship between them. With regard to discretion in law enforcement of financial legal provisions, it could also be argued that there are both legally defined irrefutable presumptions (innocence, “all doubts in favour of the taxpayer”) and rebuttable in a particular case, which does not terminate its effect as a whole. It has been concluded that presumptions on discretion in law enforcement of financial legal provisions are applied due to logical methods of induction or modelling, when the probability of a phenomenon is not high enough.