Русско-англо-русский юридический словарь

In commercial practice, particularly when transactions of considerable complexity are involved, it is quite frequent that after prolonged negotiations the parties sign an informal document called “Preliminary Agreement”, “Memorandum of Understanding”, “Letter of Intent” or the like, containing the terms of the agreement so far reached, but at the same time state their intention to provide for the execution of a formal document at a later stage (“Subject to Contract”, “Formal Agreement to follow”). (UNIDROIT PRINCIPLES 2010 )

In Russian law, there is a concept of a preliminary agreement, which is an agreement to enter into a binding agreement in future on the terms described in the pleliminary agreement. Preliminary agreement has a binding effect on the parties. Therefore, there is a risk that a memorandum of understanding, letter of intent, or any other similar arrangements, if governed by Russian law, may be treated as "preliminary agreements" and, therefore, have a binding effect on the parties. (International Stock Purchase Acquisitions: Summaries of International Law, American Bar Association, 2006, Google Books)