Shares in Sage dipped more than four per cent in morning trading on Wednesday morning after it splashed $850m (£653m) on US financial software company Intacct.
The deal is the FTSE 100 firm's biggest ever acquisition and will be funded via cash and share options.
"The acquisition of Intacct supports our ambitions for accelerating growth by winning new customers at scale and builds on our other cloud-first acquisitions, strengthening the Sage Business Cloud," said Sage chief executive Stephen Kelly.
"Intacct opens up huge opportunities in the North American market, representing over half of our total addressable market.”
Analysts at Canaccord Genuity called the deal "very expensive" and a "desperate move from management to ignite organic growth".
And analysts at Barclays said the deal signalled a move to "plan B".
In the long term this may well be the necessary acceptance that its existing business is simply behind in the cloud, however, in the near term it is another dilutive deal (following the US payments disposal) and it also confirms a change in direction from the transformation plan put in place two years ago.
It also updated investors on trading for the nine months to the end June: organic revenue was up 6.3 per cent in the third quarter and 6.4 per cent over the nine month period. It reconfirmed full-year guidance of six per cent growth.
The Intacct deal is expected to close within weeks.