The society's enlarged trading group, which will be the world's biggest consumer co-operative, is to be headed by United Co-operatives chief executive Peter Marks.
Co-operative Group chief executive Martin Beaumont, who announced last October that he would retire this year, has brought his departure forward to coincide with the merger's completion. Co-operative group food retail chief executive Guy McCracken has announced he will retire in a year, to be replaced by general food manager Tim Hurrell.
The Co-operative Group said: 'Following the overwhelming support of members of both societies, the merger will be formally completed on July 29 this year, though plans to bring the£9 billion turnover businesses together will get under way immediately with the aim of creating one business in one year.'
A decision not to appoint a deputy chief executive means that Co-operative Group's deputy chief executive Paul Hewitt has been made redundant. Director of marketing Zoe Morgan has been replaced by United's head of marketing Patrick Allen.
At United Co-operatives, head of HR Roger Fretwell and general manager for property Derek Frogg have also both announced their retirement.
Commenting on his new team and the challenges ahead, Marks said: 'Our immediate priority will be to successfully integrate the businesses and support functions of both societies and deliver commercial synergies.
'We will be building on the work already under way by improving and extending our store portfolio, continually improving our customer offer and - for the first time - driving real competitive advantage from the great work that has been done to unite the co-operative brand and engage with our customer members. With more than 4,500 retail outlets, we are the largest community retailer in the UK.'
Trading Group executive team members:
Food retail chief executive Guy McCracken, formerly Co-operative Group food retail chief executive.
Tim Hurrell, formerly United Co-operatives food general manager, has been appointed as designate pending McCracken's retirement in 12 months.
Healthcare managing director John Nuttall, formerly United healthcare general manager.
Funeralcare managing director David Hendry, formerly Group funeralcare managing director.
Specialist retail managing director Neil Braithwaite, formerly Group pharmacy managing director, bringing together in one division the travel businesses, Shoefayre, Co-operative Legal Services and End of Life Planning.
Property managing director Lynda Shillaw, formerly Group property managing director, with additional responsibility for Farmcare and Group Services.
Commercial managing director Mike Austin, formerly United services general manager, bringing together in one division Sunwin Motors, Sunwin Services, E-store and Mandate.
Director of marketing Patrick Allen, formerly United head of marketing.
HR director Richard Bide, formerly Group HR director.
Chief financial officer Bryan Portman, formerly Group chief financial officer.
Martyn Wates, formerly United chief financial officer, has been appointed designate pending Portman's retirement in September.