Getting GSTR-1 B2B vs B2C classification right decides which table an invoice lands in, whether it needs to be reported invoice-by-invoice or summarised, and whether your buyer can even see it to claim input tax credit. It sounds like a simple check, but sellers running high invoice volumes across marketplaces and direct sales get it wrong often enough that misclassification is one of the most common causes of GSTR-1 correction filings.
This article covers the actual classification test, the additional split between B2C large and B2C small, worked examples across five sample invoices, why the classification matters to your buyer, and the mistakes that show up repeatedly.
The Core Classification Test
The question that decides B2B vs B2C is not the size of the buyer or the nature of the goods; it is a single fact: is the buyer registered under GST and did they provide a valid GSTIN for this purchase? If yes, the invoice is B2B and reported against that specific GSTIN. If no, it falls into one of the two B2C categories.
A common misconception is treating 'business customer' and 'B2B' as the same thing. A registered business that buys without quoting its GSTIN, for example for goods intended for personal use rather than resale, is still reported as B2C for that transaction.
B2C Large vs B2C Small: Where the Threshold Comes In
Unregistered-buyer supplies split further based on two conditions: whether the supply is interstate (different state code for supplier and place of supply), and whether the invoice value crosses a specified threshold. Below the threshold, or for any intrastate unregistered supply, invoices are summarised by state and tax rate as B2C small. Above the threshold for an interstate supply, each invoice is reported individually as B2C large.
| Condition | Classification | How it's reported |
|---|---|---|
| Registered buyer with valid GSTIN | B2B | Invoice-level, grouped by recipient GSTIN |
| Unregistered buyer, intrastate, any value | B2C small | Summarised by state and tax rate |
| Unregistered buyer, interstate, below threshold | B2C small | Summarised by state and tax rate |
| Unregistered buyer, interstate, at or above threshold | B2C large | Invoice-level detail |
The exact rupee threshold for B2C large classification is set by GST rules and has been revised in the past, so confirm the current figure on the official GST portal at www.gst.gov.in before relying on it for a specific invoice.
Five Sample Invoices, Classified
| Invoice | Buyer | Supplier state to buyer state | Value | Classification |
|---|---|---|---|---|
| INV-101 | Registered distributor, valid GSTIN provided | Karnataka to Maharashtra | Rs. 45,000 | B2B |
| INV-102 | Unregistered individual customer | Karnataka to Karnataka | Rs. 12,000 | B2C small |
| INV-103 | Unregistered individual customer | Karnataka to Delhi | Rs. 3,20,000 | B2C large (above interstate threshold) |
| INV-104 | Unregistered individual customer | Karnataka to Delhi | Rs. 1,500 | B2C small (below threshold despite being interstate) |
| INV-105 | Registered business, GSTIN not quoted at purchase | Karnataka to Tamil Nadu | Rs. 8,000 | B2C small (GSTIN not provided, so treated as unregistered) |
Why This Split Matters for the Buyer's Input Tax Credit
A B2B invoice you file flows through to your buyer's GSTR-2B, which is the basis they use to claim input tax credit. If you misclassify a genuine B2B sale as B2C, your buyer's GSTR-2B simply will not show that invoice, and they cannot claim credit on it no matter how correct their own books are. This is usually the first sign a seller gets that something was misclassified: an unhappy buyer asking why an invoice is missing from their credit report, not a portal error on the seller's own filing.
Common Classification Mistakes
- Treating a corporate-sounding buyer name as automatically B2B without checking whether a valid GSTIN was actually captured at the point of sale.
- Applying the B2C large threshold check using order value from a marketplace report instead of the actual GST invoice value.
- Leaving a B2B invoice unclassified when the buyer's GSTIN was entered with a formatting error, causing it to silently fall into B2C.
- Forgetting to reclassify when a buyer's registration status changes mid-year, for example after they cross the mandatory registration turnover.
- Applying interstate B2C large logic to an intrastate transaction, which does not qualify regardless of value.
How OneBooks GST Auto-Classifies Marketplace Orders
When you import sales through marketplace connections for Amazon, Flipkart, Meesho, Myntra, AJIO, or JioMart, or via Excel/CSV, GSTR-1 preparation applies this classification logic automatically based on buyer GSTIN presence, place of supply, and invoice value, and flags validation warnings where a decision needs manual review. You can see the split, along with credit/debit notes and HSN summary, before export. Read more about the automated workflow on the GSTR-1 automation page, and use the GST calculator if you need to verify a specific rate or tax amount.
GSTIN Validation Before You Classify
Because the entire B2B vs B2C decision hinges on whether a valid GSTIN was captured, it is worth validating the GSTIN itself before trusting the classification, not after. A GSTIN has a fixed structure: the first two digits are the state code, the next ten characters correspond to the PAN of the business, followed by an entity code and a checksum digit. A GSTIN that is the wrong length, has a state code that doesn't match the buyer's stated address, or fails the checksum is a strong sign it was mistyped rather than genuinely invalid, and is worth confirming with the buyer before defaulting the invoice to B2C.
What to do with a GSTIN that looks inactive
Occasionally a GSTIN is correctly formatted but shows as cancelled or inactive when checked against the GST portal's search tool. Selling to a buyer whose GSTIN is not active at the time of supply is a separate compliance question from classification, and doesn't automatically make the invoice B2C; it does mean the buyer likely cannot claim input tax credit on it regardless of how it's filed, so it's worth flagging to them directly. Building this check into your invoicing workflow, rather than treating it as a once-a-year cleanup, catches inactive or mistyped GSTINs while there's still time to contact the buyer and correct the invoice before the filing deadline.
Frequently Asked Questions
What decides whether an invoice is B2B or B2C?
Whether the buyer is registered under GST and provided a valid GSTIN for that purchase. Business type or invoice size does not decide this on its own.
What is the difference between B2C large and B2C small?
B2C large applies to interstate unregistered-buyer invoices at or above a specified value threshold and is reported invoice-by-invoice. B2C small covers everything else unregistered and is reported as a state and rate-wise summary.
Does the B2C large threshold ever change?
Yes, GST thresholds are set by rule and have been revised before. Always confirm the current applicable value on www.gst.gov.in rather than relying on a remembered figure.
Why can't my registered buyer see my invoice in their GSTR-2B?
The most common reason is that the invoice was filed as B2C instead of B2B, usually because the buyer's GSTIN was missing or entered incorrectly at the time of the invoice.
Is an intrastate sale to an unregistered buyer ever B2C large?
No. The B2C large category only applies to interstate supplies above the threshold. Intrastate unregistered supplies are always B2C small regardless of value.
Can I reclassify an invoice after filing GSTR-1?
Corrections to a filed GSTR-1 are generally made through amendment tables in a subsequent period's return rather than editing the original filing directly; check the current amendment process on the GST portal.
OneBooks GST and this process
OneBooks GST is built around exactly this cycle. It produces GSTR-1 output as JSON for the portal, or as Excel and CSV for review, once validation warnings are cleared.
Keeping the original source file, the reviewed working copy and the final export together is what makes the same check repeatable next period, and OneBooks GST stores them against the filing period.
