The basic system of double entry bookkeeping was invented more than five hundred years ago by a Cistercian monk called Luca Pacioli. Every business, no matter how large or small, is required by law to ‘keep books’. This involves the recording of the financial transactions of a business, whether manually into ledgers or by entering everything onto a computer. Professional booker keeps are often certified. The Institute of Certified Bookkeepers is one such body.