Most businesses see their GSTR-1 for the first time on the portal, at which point a mistake is an amendment rather than an edit. It should be readable from your own books a week earlier, in the language of the return rather than the language of your invoices.
In short
- Where
- Books → GST summary, pick the period
- Sections
- B2B · B2CL · B2CS · CDNR · Exports · Nil-rated · HSN
- Each one
- Drills back to the invoices behind it
- Watch
- Missing GSTIN, missing HSN, and the B2CL threshold
What decides which section an invoice lands in
Three things, and none of them is chosen by hand:
- Does the customer have a GSTIN? If yes, B2B. If no, one of the B2C sections.
- Is it inter-state? Place of supply against your own state. This is also what decides IGST versus CGST and SGST.
- How large is it? Only for inter-state B2C — above the threshold it is named individually in B2CL, below it is folded into the B2CS totals.
The threshold that changed, and why the date matters
Until the middle of 2024, an inter-state sale to an unregistered buyer had to be listed individually only above ₹2.5 lakh. Notification No. 12/2024 – Central Tax, dated 10 July 2024, cut that to ₹1 lakh with effect from 1 August 2024.
The trap is not the new figure — it is that the threshold has to follow the invoice’s date, not today’s. A return being filed late for July 2024 is still judged against July’s ₹2.5 lakh. Software that hard-codes one number puts three months of invoices in the wrong section and never mentions it.
Step by step
Open the period
Books → GST summary, pick the month. Every section comes back computed from the documents themselves — not from a separate tax ledger somebody maintains.
Check B2B against what you expect
Count the registered customers you billed this month and compare. An invoice with a missing GSTIN quietly lands in the B2C figures instead, and the way you normally find out is your customer ringing about input credit.
Check B2CL
Inter-state, unregistered, above ₹1 lakh. If this section is empty and you know you had a large counter sale to another state, that is worth ten seconds of checking the place of supply on it.
Check CDNR carries the original
Every credit note should name the invoice number and date it reverses. That pairing is what lets the reduction be matched to the supply — a credit note with no original reference is one somebody will ask about.
Check the HSN summary adds up
Rate-wise taxable value and tax by HSN or SAC. If it does not tie to your total, the cause is almost always a line with no HSN on it — the summary is built from the lines, and a line with nothing to group by has nowhere to go.
Export and file
Export the return and file it on the portal, having already seen what is in it. The point of the exercise is that the portal shows you nothing you did not already know.
The bit that trips people up. Place of supply, not the customer’s address. They decide the same thing most of the time and not always — goods delivered to a site in another state, services performed where the customer is not. Place of supply is what the return uses, and it is a field on the invoice for exactly that reason.
Common questions
What is the B2CL threshold in GSTR-1?
One lakh rupees, for inter-state supplies to unregistered persons, reported invoice by invoice in Table 5. It was ₹2.5 lakh until Notification No. 12/2024 – Central Tax, dated 10 July 2024, reduced it with effect from 1 August 2024.
Which threshold applies to an old invoice filed late?
The one in force on the invoice’s own date. A July 2024 invoice is judged against July’s ₹2.5 lakh.
What happens if a customer GSTIN is missing?
The invoice is treated as a supply to an unregistered person and lands in B2CL or B2CS instead of B2B, and your customer cannot claim input credit against it.
Why does my HSN summary not tie to my total?
Almost always a line with no HSN or SAC on it.
Correct as of September 2026. GST thresholds and return formats change; confirm the current position before filing.
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