The account was previously held by tech PR firm Whiteoaks.
As well as brand promotion, Berkeley will work to position the business as the driving force behind financial cloud platforms.
John Coldicutt, CMO of IRIS, said: "Berkeley PR’s approach is refreshing; the team works hard to ensure that our messages are getting through to the right people. There are over five million private business in the UK (99 per cent are small) and over 90 per cent still use old-fashioned accounting methods. We want to arm them with the right platform to make the best decisions and collaborate effectively with their accountants."
Paul Stallard, managing director of Berkeley PR, said: "IRIS is a fantastic addition to our growing client base and we’re looking forward to the challenge of helping the brand gain the positive recognition it deserves."