GSTR-1 Reporting Errors in 2026: HSN Dropdowns, Table 12 Split and the ₹1 Lakh B2C Rule
GSTR-1 now requires HSN codes chosen from a dropdown, 4 digits up to ₹5 crore turnover and 6 digits above, a Table 12 HSN summary split between B2B and B2C, and invoice-wise reporting of inter-state B2C invoices above ₹1 lakh. Clean item masters and tag customer types to avoid rejected uploads.
GSTR-1 has changed piece by piece since 2024. Each change is small, but together they explain many rejected uploads and mismatch notices.
1. HSN digits by turnover
| Aggregate turnover in the previous year | HSN code digits |
|---|---|
| Up to ₹5 crore | 4 digits (mandatory for B2B) |
| Above ₹5 crore | 6 digits |
Since 2025, HSN codes in GSTR-1 must be chosen from a dropdown of valid codes. Codes that are not in the master are rejected.
2. Table 12 split into B2B and B2C
From the April 2025 tax period, the HSN summary in Table 12 has two tabs: one for supplies to registered persons (B2B) and one for consumers (B2C). The totals must match the invoices reported in the other tables.
3. Large inter-state B2C invoices
Inter-state sales to unregistered customers are reported invoice by invoice in Table 5 if the invoice value is above ₹1 lakh (earlier ₹2.5 lakh), from 1 August 2024. Smaller ones go in the B2C summary.
Common errors and fixes
| Error | Fix |
|---|---|
| HSN in the item master has 8 digits or old codes | Clean the item master; map each item to a valid code |
| Table 12 total does not match invoice totals | Make sure credit notes and amendments flow into the HSN summary |
| B2B and B2C mixed in one summary | Use billing software that tags each invoice by customer type |
| ₹1.5 lakh inter-state B2C invoice in summary | Report it invoice-wise in Table 5 |
| Wrong unit of measure (UQC) | Use the standard UQC list |
A worked example
A Rajkot hardware distributor's GSTR-1 upload kept failing. The item master had 410 items with 8-digit HSN codes copied from supplier bills, and some old codes. The team mapped every item to a valid 6-digit code from the dropdown list, set customer type on every party, and the next upload went through first time.
Frequently asked questions
Do composition taxpayers file GSTR-1?
No. They file CMP-08 and GSTR-4.
Does Table 12 need service codes too?
Yes. SAC codes for services go in the HSN summary.
Can I fix last month's HSN summary?
Use GSTR-1A before filing GSTR-3B for that month, or the amendment options in a later GSTR-1.
Sources
- ✓Phase III changes to Table 12 of GSTR-1, TaxScan
- ✓HSN code reporting updates, TaxGuru
- ✓B2C invoice threshold reduced to ₹1 lakh, Cashflo
This is a summary, not legal advice. Confirm with your chartered accountant.
Written by
Founder, Airwix Technologies (Sleet)
Vatsal Sutariya is the founder of Airwix Technologies in Ahmedabad, the company that builds Sleet: SleetHR for HR and payroll, and Sleet Accounting for GST billing and books. He writes about GST, invoicing, business tax and choosing software for Indian businesses, and checks each rule against the official notification before it is published.
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