Use an issue-first route when you know the problem but not the section number. Each pathway leads back to the controlling law, rather than replacing it with a checklist.
Is the composition scheme actually available to my business?
Export, LUT, place of supply and refund — how do they connect?
Person, transaction, supply, State, period and document.
Section → Rule → notification/circular → form/return.
Books, portal, invoices, tax payment and counterparty evidence.
File, reply, pay, claim, correct or appeal with a defensible evidence file.