This paper presents an analysis of legal issues related to the use of a blockchain in business. Considering the legal aspects at as early a stage as possible is one of the key areas which are crucial for the success and timely realisation of a project. The scope of legal issues depends on the type of the decentralised solution chosen by the organisation. The authors explain the differences between an open blockchain and a closed one, noting the degree of control and the advantages of both solutions. When it comes to the following paragraphs of the paper, the meaning of jurisdiction selection and the manner of managing personal data in projects related to the use of blockchain are discussed. The authors explain what smart contracts are to the reader. They point out sector regulations which may have an influence on the carrying out of blockchain projects in individual sectors that are regulated. They analyse the issues of the cryptocurrency market and explain to the readers why the taxation of cryptocurrencies is controversial. In the final part, they signal that organisations planning to implement a blockchain-based solution should take the Anti-Money Laundering (AML) regulations and related issues concerning Know Your Customer (KYC) into consideration. The paper makes it possible to understand why the legal regulations discussed may turn out to be an essential project risk if they are not recognised in time, and how addressing legal issues smoothly helps in the transformation of a project at the Proof of Concept stage, into a solution that works productively.