Checking a company's GST registration before the invoice
The panel on the Invoices tab lists the companies on your bills and bookings, and says when each GSTIN was last checked. Search for one that is not there yet.
A B2B invoice carries the customer's GSTIN, and a GSTIN can be cancelled. The GST registrations panel on the Operations → Invoices tab exists to catch that *before* the invoice prints.

- The payers — each company on a bill or a booking here, its GSTIN, its status, when it was last checked, and how many bills it has.
- Find another company by name or GSTIN — one that has not been billed here yet.
What it lists
By default, only the companies that have a bill or a booking at this hotel — a company with a guest arriving next week is exactly the one to check now. Each row says how many bills the company has here, and when its GSTIN was last checked against the government's register.
It does not list the whole corporate book. A group can hold several thousand company accounts, and a panel that draws all of them alphabetically answers "which registrations exist" when the desk's question is "which are on my invoices".
A company that is not there yet
Type its name, branch or GSTIN in the search box. The search ignores the filter above and shows what matches, up to fifty rows — more than that and it asks you to narrow it.
What to do with a stale check
Re-check it. A registration that comes back cancelled must not go on a tax invoice: the bill would be refused on the portal and the credit lost. Ask the guest for the company's current GSTIN, or bill the guest.