GST consulting is the work that happens between two returns — whether a supply is goods or services, which rate applies, where the place of supply falls, whether RCM is attracted, and how a new notification changes an existing contract. Getting this wrong is more expensive than a late fee.
Opinions are written against the invoice, the contract, and the current rate notification, so the position can be used in the next return and, if needed, in a reply to a notice.