A union that has a political fund must either—
make a separate levy of contributions to that fund from the members who are contributors, or
relieve members who are not contributors from the payment of the appropriate portion of any periodical contribution required from members towards the expenses of the union.
In the latter case, the rules shall provide—
that relief shall be given as far as possible to all members who are not contributors on the occasion of the same periodical payment, and
for enabling each member of the union to know what portion (if any) of any periodical contribution payable by the member is a contribution to the political fund.