ISD mandate under GST requires mandatory ISD registration and ISD distribution of input tax credit instead of prior flexibility.
The Finance Act amended the ISD framework to mandate ISD registration for head offices receiving services on behalf of branches and to require distribution of input tax credit through the ISD mechanism, including credits on reverse charge transactions. Cross charge remains the route for internally generated support services where suppliers must issue tax invoices and valuation follows applicable rules. Practical compliance obligations include ISD registration, separate ISD ledgers, reconciliation with portal data, pro rata distribution under the prescribed rule, filing the ISD return, issuing ISD invoices, and ERP and procedural updates. (AI Summary)

Zero-rated supply to SEZ units requires proof of authorised operations, endorsed invoices, and LUT documentation to qualify.
Supplies to SEZ units or developers are zero-rated only when intended for the SEZ recipient's authorised operations; suppliers must verify authorised use, pay tax and claim refund or supply under a Letter of Undertaking, and obtain and retain LOA, SEZ authority invoice endorsements via DPF/DSPF on the SEZ portal, recipient declarations, and include prescribed endorsement text and LUT ARN on tax invoices to preserve zero-rating and avoid tax discharge risks. (AI Summary)