GSTR-1 pre-filing checklist

Eleven checks to run on a sales sheet before you prepare GSTR-1. Each one catches an error that otherwise shows up as a portal rejection, a mismatch in the buyer's return, or an amendment next month.

By the MorGST team. Last reviewed 8 November 2026.

Numbers and parties

1. Invoice and note numbers are valid. At most 16 characters, using only letters, numbers, a slash or a hyphen, and unique in the financial year.
2. One number belongs to one document. The same number on two different dates or customers is a clash that needs fixing at the source.
3. Customer GSTINs have the right format. 15 characters: a two-digit state code, the ten-character PAN, an entity number, the letter Z and a check character.
4. No sale to your own GSTIN. It is almost always a data-entry slip.

Notes, dates and amendments

5. Credit and debit notes name the original invoice. A note to a registered buyer without its original number cannot be matched.
6. Every document is dated inside the return period. A document from another month is either reported in the right period or shown as an amendment.
7. Amendments carry their original reference. B2C (Others) amendments need the original month. Invoice and note amendments need the original number.

Tax details

8. Marketplace sales carry the e-commerce operator's GSTIN. Sales through Amazon, Flipkart or Meesho are reported against the operator, and the TCS match needs it.
9. HSN or SAC codes are present and long enough. Four digits for turnover up to Rs 5 crore, six digits above that. Check the current notification for changes.
10. No zero or negative taxable value on an invoice. Credit notes are negative by design; invoices are not.
11. Gaps in document numbering are explained. The documents-issued table needs cancelled and unused numbers to add up.

Run these checks automatically

MorGST runs these checks on every sales sheet and lists what to fix before you export the GSTR-1 JSON, Tally XML or Excel file. You still review the file and file on the GST portal. Rules change, so confirm against the official notifications.

• GSTR-1 due date: monthly and QRMP dates.
• One roof for a CA office: what MorGST covers.

Questions

What should I check before filing GSTR-1?

Invoice and note numbers, customer GSTIN format, credit and debit notes linked to their original invoice, document dates inside the period, HSN or SAC codes, marketplace operator GSTINs and amendment references.

How long can a GST invoice number be?

Up to 16 characters, using letters, numbers, a slash or a hyphen, and it must be unique in the financial year.

How many digits must the HSN code have?

Four digits for businesses with turnover up to Rs 5 crore and six digits above that. Check the current notification for changes.