It blamed slowing British consumer demand and weaker U.S. economic conditions, factors it said it expected to continue into 2018.
It reported a 8.4 percent rise in revenue to 1.27 billion pounds for the third quarter that ended Sept. 30.
Credit card processing company Vantiv secured a deal to buy Britain's largest payment processor for 8 billion pounds in August in a deal set to create a $29 billion global payments powerhouse.
Worldpay said on Monday that shareholder meetings to approve the deal would take place in early January and that it expected the deal to complete in mid-January.
The British firm was set up in 1989 and spun out of Royal Bank of Scotland to private equity firms Bain Capital and Advent International in 2010.
(Reporting by Noor Zainab Hussain in Bengaluru; editing by Jason Neely)