(in Britain) a system that encourages people to save some of their money and enables the government to borrow money from the people. It was formerly known as National Savings and before that as the Post Office Savings Bank (founded in 1861). It used to operate through post offices all over Britain, but now it operates mainly online and by mail. It offers various ways of saving and investing money, including ISAs and Premium Bonds. Many people in Britain have some money in NS&I, which raises billions of pounds for the government's Public Sector Borrowing Requirement.