Sir,
If any small sub contractor (below ₹ 20 lakh) non register can supply construction service in different state if not why, if yes then the input can take service receiver from self deposit IGST ( tax under reverse charge) , the process of reverse charge discussion.
Interstate supply registration required: small construction subcontractors must register and may claim input tax credit. Interstate supply of construction services requires GST registration irrespective of turnover; an interstate supplier cannot avoid registration by virtue of being a small contractor. When reverse charge applies, the recipient deposits tax and the supplier, if registered and eligible, may claim input tax credit as permitted under GST law. (AI Summary)