Dec 20 (Reuters) - British software company Sage Group (SGE.L) said on Monday it would buy the remaining 83% stake in cloud-based software provider Brightpearl it does not already own for about $299 million. The deal for Brightpearl, which provides operating systems to retailers and wholesalers, will be funded using existing cash and liquidity, London-listed Sage said. The British firm, whose own software helps small- and medium-sized businesses manage their accounts, payroll and other processes, said Brightpearl"s sales are expected to grow 50% to $27 million this year with operating profit set to reach breakeven. "Bringing our two teams together will help combine the retail strength of Brightpearl and the scale, brand and financial expertise of Sage," Brightpearl Chief Executive Officer Derek O"Carroll said. Sage Group, which owns a minority stake in Brightpearl, said the deal is expected to complete next month. The British company"s shares, which have risen roughly 40% this year, were trading marginally higher at 814.8 pence, by 0932 GMT, amid broader market weakness. Reporting by Amna Karimi in Bengaluru; Editing by Shounak Dasgupta and Sherry Jacob-Phillips