Portfolio revision is the process of adjusting the composition of securities or bonds in a portfolio depending on the performance, expectations, and strategy. It involves selling certain securities in a portfolio and purchasing new ones to maximize returns and minimize risk. The need for portfolio revision arises when an individual has some additional money to invest or when there is a change in investment goal. There are two types of portfolio revision strategies: active revision strategy and passive revision strategy. Active revision strategy involves frequent changes in an existing portfolio over a certain period of time for maximum returns and minimum risks, while passive revision strategy involves rare changes in a portfolio only under certain circumstances. Formula plans are certain predefined rules and regulations deciding when and how much assets an individual can purchase or sell for portfolio revision. Portfolio revision is important in investment portfolio management as it helps to adjust the existing portfolio in accordance with the changes in financial markets and the investors position to ensure maximum return from the portfolio with the minimum of risk.