Private equity firm Advent owns the group after spinning it out from Lloyds TSB in 2007.
It started life administering British Army pensions in 1836. The firm, based in the seaside town of Lancing, paid out £90 billion to 27 million people in the UK last year and does work for about 70 companies on the FTSE 100.
Other firms joining the rush to market include insurer Hastings, payments group Worldpay and brick maker Ibstock.
