Members of Penrith Co-operative have voted overwhelmingly in favour of the proposals after Scotmid had previously ratified the move on August 13.
The merger combines Scotmid's 350 retail and service outlets, including convenience stores and Semichem toiletries chain, in Scotland and the north of England, with Penrith's nine shops and Post Offices in Cumbria and County Durham.
With Scotmid serving grocery stores in Inverness, and Semichem outlets as geographically disparate as Thurso and Carlisle, a spokesman said the merger did not present any geographical barriers. But he added it was notable because it was Scotmid's first move into England as a food retailer in its 150-year history.
He also said it could lead to further expansion for Scotmid in England, stating that it put the society on the radar of companies potentially looking to sell.
The merger builds on a working relationship that has seen the two parties share ideas on areas such as IT. Although Scotmid is the bigger organisation, turning over £428 million compared with Penrith's £13m, the spokesman insisted the merger was "not one-sided". Scotmid has a strong community presence, including a grants scheme, that he said could be combined with Penrith's innovations in areas like membership.
The spokesman said: "It will be a learning process for both societies, because they have got some good things in the way they operate."
The Penrith stores will not trade as Scotmid, however. A consultation has been launched to identify a name.