Study material

GST Returns made simple: GSTR-1 and GSTR-3B

Read this before practising. GSTR-1 tells the government what you sold. GSTR-3B works out how much tax you must actually pay after using the credit on your purchases. Every table below is explained in everyday language with the mistake students usually make.

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GSTR-1 — Sales statement

What is GSTR-1?

GSTR-1 is the sales statement. Every registered business tells the government the details of the invoices it issued during the month or quarter.

Filed monthly by 11th of the next month (QRMP taxpayers file quarterly by 13th).
Nothing is paid with GSTR-1 — it is only a declaration of outward supplies.
Whatever is reported here flows into the buyer's GSTR-2B, so it decides their input credit.

Common mistake: Forgetting to file a NIL GSTR-1 in a month with no sales. It is still compulsory.

Table 4A — B2B invoices

Sales made to another registered business. Each invoice is reported one by one with the buyer's GSTIN.

GSTIN must be 15 characters; the first two digits are the buyer's state code.
Invoice number and date must match the invoice actually issued.
Place of supply decides IGST (other state) versus CGST + SGST (same state).

Common mistake: Typing a wrong GSTIN — the credit then reaches the wrong buyer and cannot be undone easily.

Table 7 — B2C (small) supplies

Sales to ordinary customers who have no GSTIN. These are not listed invoice-wise; only a total per state and per tax rate is given.

Group all small retail sales by state and by rate.
No customer name or invoice number is needed here.

Common mistake: Entering each retail bill separately instead of one consolidated figure per rate.

Table 12 — HSN summary

A short summary of what was sold, using HSN codes for goods and SAC codes for services.

Give quantity, unit (UQC) and taxable value against each code.
The total taxable value here should agree with the invoice tables.

Common mistake: HSN total not matching the invoice total — the portal flags this immediately.

GSTR-3B — Summary and payment

What is GSTR-3B?

GSTR-3B is the monthly summary return where tax is actually calculated and paid. No invoice details — only totals.

Due on the 20th of the next month for monthly filers.
Tax = output tax on sales minus eligible input tax credit on purchases.
The return cannot be filed until the balance tax is paid in cash.

Common mistake: Filing GSTR-3B without first checking GSTR-2B, so credit is claimed that the supplier never reported.

Table 3.1 — Outward supplies

Total sales of the month, split into taxable, zero-rated, exempt and reverse-charge.

Taxable sales carry IGST or CGST + SGST depending on the place of supply.
Exempt and nil-rated sales are reported but carry no tax.

Common mistake: Showing an inter-state sale as intra-state — the wrong state then gets the money.

Table 4 — Input tax credit

Credit of the GST already paid on purchases and expenses used for the business.

Claim only what appears in GSTR-2B and only for business use.
Ineligible credit (personal use, blocked items) must be reversed.

Common mistake: Claiming credit on blocked expenses like personal travel or food bills.

Table 6.1 — Payment of tax

Output tax minus credit gives the net amount. That balance is paid in cash along with interest and late fee, if any.

IGST credit is used first, then CGST and SGST credit against their own heads.
Late fee applies per day of delay; interest is charged on tax paid late.

Common mistake: Assuming unused credit lapses — it is carried forward to the next month.

Quick revision

GSTR-1 = what I sold. GSTR-3B = what I must pay.
GSTR-1 by the 11th, GSTR-3B by the 20th of the next month.
Same state sale → CGST + SGST. Other state sale → IGST.
Tax payable = output tax on sales − eligible input credit on purchases.
NIL returns must still be filed, otherwise late fee keeps adding up.