The new law is part of Medvedev's efforts to clamp down on corruption in Russia, which he made a priority soon after his inauguration in May.
Tax authorities must be allowed access to information about ministers' incomes, as well as any stocks and property held in their name or by their spouses or minor children.
The prime minister, deputy prime ministers and Cabinet ministers are all affected by the law, which was passed by the State Duma on December 19 and the Federation Council on December 22.
The president has also signed two laws limiting checks on business activity by the police, which can be used to solicit bribes or to harass small business owners, and protecting the rights of individuals and entrepreneurs regarding state control and supervision of their activities, the press service announced.
