GST Filing for E-Commerce Sellers: A Founder's Guide (No CA Needed)

If you sell online in India and you're paying a CA ₹5,000–₹15,000 every month to file your GST returns, this post is for you. It's not because CAs are bad — most of the work in monthly GST filing is form-filling once your invoice data is clean, and you can do that part yourself. The CA's value is in the 10% that's actually hard. This post walks you through the 90%.

Why ecommerce sellers have it harder

A general SMB filing GSTR-1 deals with maybe 50–200 outward supplies a month, mostly to a handful of B2B clients in one or two states. An ecommerce seller dealing on Shopify + Amazon + Flipkart + Meesho deals with:

500–5,000 invoices a month, each in a different state, each with different tax treatment
Multiple platforms, each with its own TCS deduction (1% by default)
COD vs prepaid handled differently
RTO returns that need credit notes
Marketplaces that report your GSTR-1 data on your behalf to GSTN under section 52
Cross-state movements where place-of-supply rules trip up first-time filers

The CA isn't expensive because the work is hard. The CA is expensive because there's a lot of it.

The good news: tooling makes the volume manageable. You don't actually need a human to type 5,000 invoices into the GSTN portal. You generate the GSTR-1 JSON from your order data, validate it, upload it. Then GSTR-3B is a summary that auto-populates from GSTR-1. The CA's actual judgment work — RCM corner cases, ITC reconciliation, notice handling — is a much smaller surface than the entire monthly cycle.

The two returns that matter every month

For 99% of ecommerce sellers, monthly GST = filing two returns:

GSTR-1: outward supplies. Every invoice you issued in the month, with HSN code, taxable value, and GST split (CGST/SGST or IGST). Filed by the 11th of the following month for monthly filers, or by the 13th of the quarter-end month for quarterly filers under QRMP.

GSTR-3B: a summary. Total outward, total tax collected, ITC claimed, tax paid. Filed by the 20th of the following month. This is the return you actually pay tax against.

There's also GSTR-2B (auto-populated from your suppliers' GSTR-1, shows your eligible ITC) but you don't file it — you match against it.

Place-of-supply: the rule that gets first-time filers in trouble

Here's the rule, simplified:

If you (the seller) and the buyer are in the same state: it's intra-state. CGST + SGST.
If you're in different states: it's inter-state. IGST.

Sounds simple. Where it gets ugly:

The buyer's "state" is determined by the shipping address, not the billing address.
If a Karnataka-based seller ships to a Delhi address with a Mumbai billing address, the place of supply is Delhi → IGST.
For digital goods/services delivered to an address-less buyer, the rule is the buyer's location of consumption, which gets thorny.

Practical implication for ecommerce: always pull the shipping state from your platform's order data, not the billing state. Most order-management tools default to billing for tax calculations and that's wrong for ~5–8% of orders.

TCS reconciliation: the marketplace gotcha

Under Section 52 of the CGST Act, marketplace operators (Flipkart, Amazon, Meesho, etc.) deduct 1% TCS on the net taxable value of your sales through them. They report this in their GSTR-8, which then shows up in your GSTR-2A as a TCS credit you can claim against your GSTR-3B.

Two things go wrong:

The marketplace's TCS amount doesn't match your records. Maybe their commission was deducted before TCS was calculated, or returns weren't netted out. You need to reconcile and dispute through the marketplace's seller panel.
You forget to claim the TCS credit. It's not auto-applied; you have to enter it in GSTR-3B's "TCS credit available" field. If you don't claim it that month, you can claim it later, but it's working capital you don't have to lose.

If you sell on 3+ marketplaces, the reconciliation alone is 4–6 hours of work per month. This is what the CA is being paid to do — and what tools can automate.

A monthly filing schedule (the actual one)

Here's how a real ecommerce seller's GST month flows:

Day of month	Activity
1–10	Continue running the business; invoices auto-generated from orders
5	Pull provisional GSTR-1 draft for the previous month, scan for obvious errors
8	Match GSTR-2B (eligible ITC from suppliers) against your purchase records
9	Reconcile TCS from each marketplace against your sales records, dispute mismatches
10	CA reviews the GSTR-1 draft (if you have one) — this is the actual high-value CA work
11	File GSTR-1
13	Recipients can see your GSTR-1 in their GSTR-2B
18	Pull provisional GSTR-3B; verify tax liability and ITC claim
19	CA reviews GSTR-3B if engaged
20	File and pay GSTR-3B

The "real CA" work is the review on day 10 and day 19. Everything else is form-filling that automation can do.

CA vs DIY: real cost comparison

Here's an itemized comparison for an ecommerce seller doing ₹15 lakh of monthly GST-able revenue across 3 marketplaces:

Approach	Monthly cost	Time you spend	Risk
Full CA retainer	₹8,000–₹15,000	1–2 hours/month (CA emails you docs)	Low (CA's responsibility)
DIY filing	₹0 (just GSP fees if e-invoicing)	6–12 hours/month	Medium (you own errors)
Software + hourly CA review	₹1,500 software + ₹3,000 CA review	2–3 hours/month	Low (CA reviews before submit)
Software only, no CA	₹1,500 software	3–5 hours/month	Medium

The hybrid (software + hourly CA review) is the right answer for most ecommerce sellers. You save ₹4,000–₹10,000/month and your error risk is the same as a full CA retainer because the CA still reviews before you submit.

The full DIY path is for founders who genuinely understand GST or have a small enough operation that errors are caught quickly. Don't go full DIY in your first year — get the patterns right with a CA backstop, then let the CA go after 6–12 months once you trust your tooling.

Tools that auto-draft your returns (and what to look for)

Several Indian tools draft GSTR-1 and GSTR-3B from your order data. The key features to evaluate:

Multi-marketplace ingest: Can it pull orders from Shopify + Amazon + Flipkart + Meesho automatically? Or do you have to upload CSVs every month?
TCS reconciliation: Does it match marketplace TCS reports against your sales and surface mismatches?
JSON export for GSTN portal: Some tools file directly via GSP API. Others export a JSON you upload manually. Both work; the difference is one fewer step.
HSN code lookup: Auto-suggest HSN codes for your products if you haven't classified them yet.
Place-of-supply logic: Does it use shipping state, not billing state?
Credit notes for returns: Can it handle marketplace returns/RTO as credit notes against the original invoice?

ClearTax, Zoho Books (with GST module), Tally Prime, and Doggu all do most of these. Doggu's specifically designed around the multi-marketplace ecommerce flow, while ClearTax is the most established for general GST. Pick based on your existing stack.

Edge cases that actually need a CA

Here's where the human matters:

GST notices: A reply to a Section 61 scrutiny notice or a Section 73/74 demand notice needs a CA. Don't try to draft this yourself.
Refund claims: Refund of inverted duty structure or refund on exports has tricky paperwork.
Annual GSTR-9 + 9C: The annual return + reconciliation is genuinely complex for businesses above ₹2 crore turnover. Worth paying a CA for this even if you DIY monthly.
RCM corner cases: If you import services or buy from unregistered dealers, the reverse charge mechanism applies. Get this wrong and ITC is denied.
Composition scheme decisions: Whether to opt for composition vs regular is a real strategic call.
Input service distributor questions: If you're spread across states, ISD vs cross-charging is a CA decision.

These are the things you pay a CA for. Not GSTR-1 typing.

Frequently asked questions

How much can I realistically save by going hybrid?

If you're paying ₹10,000/month for a CA retainer, you can typically get to ₹4,500/month total (software + hourly CA review) without losing any quality. ₹66,000/year saved.

What happens if I file GSTR-1 wrong?

Up to a point, you can amend in the next month's GSTR-1A. Beyond that, errors carry forward and can trigger notices. The cost of fixing a wrong GSTR-1 is ~3–5x the cost of getting it right the first time, which is why the CA review on day 10 is worth keeping.

Can I file GSTR-1 and GSTR-3B from a software, or do I have to use the GSTN portal?

Both work. GSPs (GST Suvidha Providers like ClearTax and Cygnet) have API access to file directly. You can also generate JSON from a tool and upload manually on the GSTN portal. Either is fine.

Do I need e-invoicing?

If your aggregate turnover crossed ₹5 crore in any past financial year, yes. The threshold has been progressively lowered (was ₹500cr in 2020, ₹5cr from 2023). Below ₹5cr, e-invoicing is optional but increasingly common.

What's the worst-case penalty if I miss a filing?

Late fees: ₹50/day for GSTR-1 (₹20 if nil), capped at ₹5,000. ₹50/day for GSTR-3B. Plus interest at 18% on unpaid tax. Plus a registration cancellation if you skip 6 consecutive returns. The downside is real; don't be casual about deadlines.

If you want to see what your monthly filing would look like drafted automatically from your Shopify/Amazon/Flipkart orders, Doggu's GST module is built around this exact flow — drafts GSTR-1, reconciles TCS, exports GSTN-ready JSON. Or just play with our free GST calculator to verify your manual math.