GST procedural amendments expand challan rules for job workers and clarify Authority powers on investigations and decision-making. The amendment expands challan mechanics for job workers, allowing principals or sending job workers to issue challans and for sequential endorsements by intervening job workers; designates the Secretary to the Authority as an officer not below Additional Commissioner; permits the Authority to refer matters back to the Director General of Safeguards for further investigation; clarifies quorum and majority decision-making with chairman's casting vote; adds a complaint ground alleging failure to pass on tax-rate reductions or input tax credit benefits; and excludes leasing of railway parcel space from 'transport of goods by rail' for the Chapter.