How to File GST in India (GSTR-1 & GSTR-3B)

How GST works in India

Goods and Services Tax (GST) is India's unified indirect tax, administered by the Central Board of Indirect Taxes and Customs (CBIC) through the GST Network (GSTN) portal. It replaced a patchwork of older taxes with one system charged at each stage of supply, with credit for the tax you paid on your own inputs.

GST is genuinely multi-rate. The main slabs are 5% (merit/essentials), 12%, 18% (the effective standard rate for most goods and services) and 28% (demerit/luxury), with special rates for items like gold. Getting the right rate on each product matters, because it flows through to your returns.

Who must register

Registration is generally mandatory once turnover exceeds ₹40 lakh for goods or ₹20 lakh for services (lower thresholds apply in special-category states). Some businesses must register regardless of turnover — for example inter-state suppliers, e-commerce operators, and those under reverse charge.

Once registered you receive a 15-digit GSTIN, which must appear on your tax invoices.

Filing GSTR-1 and GSTR-3B, step by step

1. 1

   Reconcile your sales and purchases

   Total your outward supplies by GST rate and gather your purchase invoices so you can claim input tax credit. Clean bookkeeping software that tags GST on every sale makes this a few clicks rather than a spreadsheet marathon.

2. 2

   File GSTR-1 (outward supplies)

   Log in to the GSTN portal and report your outward supplies in GSTR-1 — invoice-wise for B2B and summary for B2C. This feeds your customers' input-tax credit, so accuracy matters. It is filed monthly, or quarterly under the QRMP scheme.

3. 3

   File GSTR-3B (summary & payment)

   GSTR-3B is the summary return where you declare your total output tax, claim eligible input tax credit, and pay the net GST due. Reconcile it against GSTR-1 and your auto-drafted GSTR-2B before submitting.

4. 4

   Pay the net tax

   Pay any balance through the portal's electronic cash ledger. Late filing attracts interest and late fees, so file on time even for a nil period.

E-invoicing (IRP)

Businesses above the notified turnover limit must generate e-invoices: your invoice data is sent to the Invoice Registration Portal (IRP), which returns a unique Invoice Reference Number (IRN) and a QR code and auto-populates parts of GSTR-1 and the e-way bill. This is general information — the applicable turnover limit has been lowered in stages, so confirm whether it applies to you.

How Tallium helps

Tallium tags the correct GST rate on every sale and expense as you trade, keeps your input-tax credit organised, and builds GSTR-1 and GSTR-3B-ready summaries so filing on the GSTN portal is a review rather than a rebuild. Always confirm current rules with the CBIC or a qualified tax professional before you file.