How to Calculate GST Payable on Marketplace Sales (Worked Example)

After a big sales month, the question is not "how much did I sell". It is "how much GST cash do I need to hand over, and when". The answer is a short subtraction, and sellers who work it out before the 20th are not caught short.

Or skip the arithmetic: the GST payable calculator does this for two months at once. This guide shows what it is doing.

The formula

GST cash to pay = output GST − ITC on purchases − ITC on marketplace fees − TCS credit

• Output GST is the tax on what you sold, after returns and cancellations.
• ITC on purchases is the GST you paid your suppliers, claimable when it shows in your GSTR-2B.
• ITC on marketplace fees is the 18% GST the platform charges on its commission, fixed and shipping fees.
• TCS credit is the 0.5% the marketplace collected on your net taxable sales.

Worked example: one month, all at 18%

Suppose you sold ₹5,00,000 in a month on a marketplace, after returns, and prices include GST.

Step	Working	Amount
Taxable value of sales	5,00,000 ÷ 1.18	₹4,23,729
Output GST	5,00,000 − 4,23,729	₹76,271
ITC on purchases	You bought ₹2,50,000 of goods incl. 18% GST: 2,50,000 × 18 ÷ 118	−₹38,136
ITC on marketplace fees	Fees of ₹60,000 before GST × 18%	−₹10,800
TCS credit	0.5% of ₹4,23,729	−₹2,119
GST cash to pay		₹25,216

Of the ₹76,271 you collected on sales, about a third reaches the government in cash. The rest is offset by credits you can only use if they are correct and visible in your portal.

Where the numbers come from

1. Sales and returns. Use your marketplace's monthly tax report, not the payout, because the payout is after fees and TDS. Returns and cancellations reduce your output GST, but only in the return where you record the credit note.
2. Purchases. Take the GST from supplier invoices that appear in your GSTR-2B. An invoice your supplier has not reported does not give you ITC, however valid your copy is. The GSTR-3B guide covers reconciliation.
3. Fees. Download the platform's tax invoices for its fees. Check they carry your GSTIN.
4. TCS. The marketplace reports it in its GSTR-8, due by the 10th of the following month. See how to claim TCS on Amazon and Flipkart for where it shows up. If it is not there yet, do not assume it.

What changes the answer

• Mixed rates. Sales at 5% and 18% carry different tax, so compute each slab separately or use a blended rate. Check your product's HSN rate before you assume one.
• A big return wave. Festive returns often arrive in the next month. Credit notes cut that month's liability, so this month's cash can be higher than the final position.
• Interstate vs local sales. The tax splits into IGST or CGST plus SGST, and credits are used in a set order. The total does not change here, but which ledger pays does.
• Lost or blocked ITC. Anything not in GSTR-2B, or blocked under Section 17(5), pushes your cash payment up.

Plan the cash before the 20th

If the result is more than you can spare, plan the gap early, because marketplace payouts may not land before the due date. A working-capital option is worth comparing before the deadline, and late payment costs interest and fees: see the GST late fee calculator.

Your CA partner can confirm the final figure before you file. The steps above only estimate it, so check ITC and TCS in your portal on the day you pay.

Related: GST due dates, marketplace profit calculator, festive selling guide.