GST to be paid by Housing Society members

In the prospective of the GST , If unregistered supplier has made repair work at your housing society of Rs 50/- Lacs , then he liable to take GST registration and issue your Housing society a GST Tax invoice, because threshold limit to obtain GST  registration for taxable service provider as per section 22 of the CGST act is 20 Lac , and you have paid him 50 Lac , which is more than 20 Lac . Not only this work , considering other work he may have crossed his Turnover, over and above 20 Lac . He can not keep himself  as unregistered, ones he crossed threshold limit , he has to obtain GST registration. 

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Thank you sir for your reply.

This supplier has hired individual sub-contractors and assigned them work and payments have been made to sub-contractors in their personal accounts. Since those sub-contractors are also not registered under GST, will there be any problem for the society

Who issued bill to the Housing Society ?. Supplier or Sub Contractors . please elaborate in detail.