GST registration not taken

What service

It's Labour supplier..

Service provider has to discharge tax liability underFCM

From FY 18-19 itself??

P.S. recipient is also GST registered from 2017

Manpower supply is not covered under reverse charge. GST on security services was applicable from 1st of July 2017 on forward charge but it has been brought under Reverse Charge Mechanism (RCM) from 1st January 2019 vide Notification No. 29/2018- Central Tax (Rate) dated 31/12/2018.

LAPSE on the part of service provider to collect GST while the service provider was covered under forward charge does not make the recipient liable for anything. Instead, the service provider if caught will be liable to pay 18% gst from his own pocket. and the service receiver can commercially get away without paying a single penny to the service provider towards the GST error on his part.

First read the relevant sections of rcm.

U can avail basic exemption of 20LAKHS

That was always there since 2017.

Now service provider is willing to take GST registration as manpower supplier, but does these previous defaults affect him or recipient. As recipient is worried for such big burden of tax & interest, penalty thereon since FY 2018-19 

Recipient need not worry at all.