Students, undertakers and supermarket customers will all be represented in a key poll on the future of the Co-op but none will have an individual ballot.
Block votes will decide whether the troubled food-to-funerals group takes a crucial next step towards a radical shake-up seen as vital to securing its future.
The poll will canvass support on four key principles taken from a reform plan drawn up by former City minister Lord Myners, and must achieve a simple majority of over 50% to be taken forward.
However, detailed implementation of the proposals, which would involve changes to the rules governing the mutual and have yet to be set out in full, would require a further poll which would need to see them achieve two-thirds backing.
The byzantine voting structure includes a 22% share for independent societies and affiliated organisations, and the rest made up of regional boards, elected by the Co-op's area committees.
There are five main independent societies that make up the first part - the largest of which is the Midcounties Co-operative, which operates gas and electricity supplier Co-operative Energy as well as Co-op branded food stores and other businesses.
This is seen as important because one of the four key principles of the resolution being voted on is that of "one member one vote", though with "appropriate representation for independent Co-operative societies".
Details of how this caveat will be reconciled with the main principle, which might otherwise be seen as threatening the societies' power, have yet to be produced.
Other organisations within this strand include the National Union of Students, the Co-operative Party - which is affiliated to Labour - and smaller independent societies.
The 22% voting chunk is divided among these based on how much trade they have done with the Co-op group.
Within the 78% portion representing the seven regional boards, percentages are allocated on the basis of how much money is spent at Co-op shops and other businesses within the region.
These boards will have taken soundings from the millions of individual members who are represented via area committees. Members in London are reported to have voted to reject the Myners proposals.
The Co-operative annual general meeting (AGM) takes place this morning at its head office in Manchester, followed by a special general meeting (SGM) when a vote on the Myners resolution takes place.
Lord Myners published a report earlier this month urging the group to back radical reforms to sweep away the "dysfunctional" board which oversaw a year of record £2.5 billion annual losses in 2013.
Former Treasury mandarin Sir Christopher Kelly has also recently published a scathing report on the Co-op saga, focusing on the near-collapse of its banking arm which was chiefly responsible for the wider group's woes.
Both men will speak at the SGM but only after the vote has been held.