A company, if so authorised by its articles, may—
make arrangements on the issue of shares for a difference between the shareholders in the amounts and times of payment of calls on their shares;
accept from any member the whole or part of the amount remaining unpaid on any shares held by him, although no part of that amount has been called up;
pay a dividend in proportion to the amount paid up on each share where a larger amount is paid up on some shares than on others.