The company is expected to seek a valuation of over £5bn.
After four years under private ownership Misys is returning to the London markets.
The software company was acquired by Vista Equity Partners in 2012 for £1.3bn but is now set to float for a target valuation of £5.5bn.
Misys is a provider of financial services software covering areas like corporate banking, lending, treasury, capital markets, investment management and enterprise risk.
Before its acquisition in 2012 the company had been facing difficulties with a 12% drop in its fiscal third quarter and a 3% drop for the year. Since then the company is said to be in better condition, according to Vista Equity Partners.
The company is planning to sell around £500 million of stock in an initial public offering with the trading to begin on the London Stock Exchange in November, Misys said.
According to data compiled by Bloomberg it is a good time for Misys to try and take advantage of investor demand for software stocks. European companies that are focused on application software and are valued at $1bn or more have seen a return of 14% on average.
Misys said that the money from the sale will go towards repaying existing debt, which is said to total around $1.8bn.
The float, which is being brought to the market by Goldman Sacks, Bank of America, Merrill Lynch and JPMorgan, would be the biggest of the year in the UK.
Misys is hardly the same company that was acquired in 2012, it has been merged together with Sophis, another financial software seller, and Turaz, a banking software company.
The company reported revenue of $909 million for the year ending 31st May.