We do not know whether you represent Management or trade union.
From the Management angle I would explain check off system in a factory. When two or more trade unions are in the factory, you need to decide upon the bargaining agent for any negotiations on wages and welfare of workers. The Trade Union Act paves the way to decide on how to select a trade union as a bargaining agent for workers by formulating rules under check off system.
The union office bearers are to be asked to declare their members list to management for deduction of subscription fees from the wages of workers monthly so that the management will come to know which union is holding majority among them and also to declare subscription fees.
As per the list the Management deducts monthly for the wages of workers and transfer the amount to the Union so that a proof is acquired on the Union which gains majority among workers. All communications between the management and union always in writings so that if any dispute arises on the issue of membership of worker, bargaining union, would be sorted out as per statute.