GST guides
Short, sourced explanations. Each shows the date we last checked it and links to what it's based on.
- GSTR-1 JSON over 5 MB: how to split it for the GST portalThe portal rejects GSTR-1 JSON files over 5 MB. What the limits are, how to split a file safely, and how to check the portal's totals afterwards.
- How the GSTIN check character works, and why it catches typosThe last character of a GSTIN is calculated from the other 14. How the calculation works, what it proves, and what it doesn't.
- IMS: what Accept, Reject and Pending do to your input tax creditThe Invoice Management System lets you act on supplier invoices before GSTR-2B is generated. What each action does and the deadlines that matter.
- GST rates after 22 September 2025, and what they mean for your invoicesThe 12% and 28% slabs were removed on 22 September 2025. Which rates apply to which invoice dates, and the portal error you'll see if you get it wrong.
- GSTR-3B Tables 3.1 and 3.2 are auto-filled. How to correct themOutward supply tables in GSTR-3B are populated from your GSTR-1 and can't be edited. Where to fix mistakes instead.
- GSTR-2A vs GSTR-2B: which one to use for input tax creditGSTR-2A keeps changing through the month and GSTR-2B is a fixed statement. What each shows, when 2B is made, and how to use them together.
- GST return due dates: monthly, QRMP, and why GSTR-3B has two datesThe 11th, 13th, 20th, 22nd and 24th explained: which GSTR-1 and GSTR-3B date applies to a monthly filer and to a quarterly (QRMP) filer in each state.
- GST late fee and interest: how each is worked outThe daily late fee for GSTR-1 and GSTR-3B, its caps, and the 18% and 24% interest under Section 50. Two charges, two formulas, and what is paid how.
- GST invoice numbers: the 16-character rule and how to number a seriesRule 46 says what an invoice number can contain, how long it can be, and that it must be unique. How to design a series that the GST portal accepts.
- IGST or CGST and SGST? How the place of supply of goods decidesFor goods, the tax you charge follows the place of supply. Where the movement of goods ends, and what changes when a third party directs the delivery.
- ITC reversal under Rule 42 and 43: the formula, step by stepWhen inputs serve both taxable and exempt supplies, part of the credit has to be reversed. The Rule 42 and 43 working with C1, C2, D1, D2 and C3, and a worked example.
- GSTR-1A: correcting your GSTR-1 after you've filed itGSTR-1A lets you amend or add records to a filed GSTR-1 for the same period, until you file GSTR-3B. Who can use it, how often, and what happens to GSTR-3B.
- E-invoicing and GSTR-1: why your e-invoices appear without being enteredWho must issue e-invoices, the 30-day reporting window at ₹10 crore, and why IRN invoices flow into GSTR-1 so you shouldn't upload them again.
- How to choose online GST software: a checklist for small businesses and CAsFiling on the portal, preparing files, matching purchases and billing are different jobs. What to look for, and the questions that separate the tools.