Membership shares have a dual nature: they grant members a right to vote and they contribute to the working capital a co-operative needs to finance its business. Because of this dual nature, the membership share and the minimum capital contribution required from members must be financially affordable to those who need a co-operative's services. It should not be a barrier to membership. If set too high, it risks breaching the 1st Principle of open membership. If set too low, it risks devaluing the involvement related to membership and neglecting the potential of members as a source of capital. Some jurisdictions allow for co-operatives to be established without share capital, with rights of membership established by members using the services of the co-operative.

The basic principle is that a single share, or a minimum number of capital shares set by the members' general assembly of a co-operative, or in jurisdictions which permit it, use of the co-operative is required of all members to have voting rights.

Co-operatives, like all business enterprises, require capital to finance and develop their businesses. Raising capital from members is to be favoured, but the return on members' basic capital shares that grant voting rights should be limited. A return on capital may be justified to compensate members for its use by the co-operative or loss of true value through inflation, but this 3rd principle requires such compensation to be limited. If it is not, the requirement to generate a return on members' capital beyond that needed to maintain its relative value will reduce a co-operative's operating surplus and prevent it from developing its business.

However, sources of capital other than that which can be raised from members' basic voting shares may be required by a co-operative. The preferred way to raise additional capital is to enable members who are willing and have ability to do so, to subscribe to additional capital shares without voting rights. Capital or long-term investment without voting rights, sometimes called "non-voting shares" may receive guaranteed compensation at a "fair market rate or compensatory rate" to give a reasonable return for investing without increasing control. The "fair market rate or compensatory rate" also serves as an inducement to members to invest more than their minimum voting share.

What constitutes a "fair market rate or compensatory rate" is for members to decide in general assembly in light of the capital needs of the co-operative and the financial market conditions in which it is raising capital from its members. In some countries regulators are concerned that what may be deemed by some co-operators to be "a fair market rate or compensatory rate" may simply attract speculative capital investments. The guiding principle of what is "a fair market rate or compensatory rate" remains "the lowest rate which would be sufficient to obtain the necessary funds".

Should a member wish to withdraw non-voting capital invested in a co-operative, he/she may recover his/her share capital, without specific approval of the general assembly, and receive an amount to be determined by the co-operative itself, ensuring a return on the co-operative member's participation towards enriching the co-operative. This amount may not be so high as to endanger the co-operative's financial stability. Subject to any national regulatory requirements, the co-operative in general assembly should approve the notice period required and the terms on which members may withdraw non-voting capital.