Four buckets, one report
GSTR-1 doesn't list every sale the same way — it sorts each invoice into one of four sections: B2B (the customer has a GSTIN), B2C Large (a bigger inter-state sale to a customer without one), B2C Small (everything else sold to consumers), or Export.
The bucket an invoice falls into changes how much detail the return needs — B2B invoices are reported individually with the customer's GSTIN, while B2C Small sales are usually summarised together.
What actually decides the bucket
The customer's GSTIN status is the first fork: present and valid means B2B. No GSTIN means the sale falls into a B2C category, and whether it's Large or Small depends on the invoice value and whether it crossed state lines.
Export invoices are their own category regardless of value, since the goods or services leave India and follow separate GST treatment (typically zero-rated).
A customer with a GSTIN but who forgets to share it at billing time still counts as B2C until the GSTIN is added — which is why validating it at entry matters.
LedgrBook handles this automatically. The parts of this guide your bills already know.
See how →Why this matters beyond the return
Getting the classification right isn't just a filing formality — a B2B sale marked as B2C denies your customer the input tax credit they were expecting, which tends to become your problem the moment they notice.
Software that classifies automatically from the customer's registration and the sale details — rather than asking a biller to choose — removes this as a manual judgment call.
General information, not professional tax advice — confirm specifics with your CA.
