GST Filing — GSTR-1, 3B, 2B reconciliation, e-invoice & e-way bill

The full GST cycle for an Indian SMB. Booksmor reads your posted sales and purchase vouchers, prepares the GSTR-1 and 3B returns, reconciles your input credit against GSTR-2B from the portal, and generates IRN / e-way bills for the invoices that need them.

Time to read: ~15 minutes. You’ll need: GST enabled in Settings, your home state set, posted sales and purchase vouchers for the period you want to file, and (for the actual upload) your GST portal credentials — or your CA’s help to do that part.

What you get when this is done

• A monthly (or quarterly under QRMP) GSTR-1 ready to file — every outward supply categorised correctly (B2B vs B2C, intra vs inter-state, HSN summary).
• A GSTR-3B preview that nets your output GST against eligible input credit so you know what you owe before you file.
• GSTR-2B reconciliation that flags supplier invoices on the portal that don’t match your books (and vice versa) — the #1 cause of input-credit losses.
• e-Invoice (IRN) generation for sales invoices that legally require it.
• e-Way bill generation for goods movements above the state threshold.
• A complete ITC register and RCM register for the period.

Where to find the screen

From the sidebar: GST (top-level item, between Reports and the Daily group).

The page is organised as five cards, top to bottom:

1. GSTR-1 (outward supplies) — your monthly sales return.
2. GSTR-3B (net tax) — the summary return that pays the tax.
3. GSTR-2B reconciliation — match your purchases against what suppliers declared.
4. ITC register & RCM — input credit and reverse-charge supplies for the period.
5. e-Invoice & e-Way bill — for posted sales vouchers.

At the very top: Return period (YYYY-MM or Qn-YYYY) — e.g. 2026-04 for April 2026, or Q1-2026 for Apr–Jun 2026 under QRMP.

Booksmor runs against a built-in GSP simulator by default — figures are real (sourced from your live vouchers), transmission is simulated. When you connect a live GSP (GST Suvidha Provider) on the platform side, the same buttons start hitting real endpoints.

Monthly filing — the recommended order

1. Set the period at the top — typically last month (e.g. file April’s return in May).
2. Prepare GSTR-1.
3. Preview GSTR-3B to see what you’ll owe.
4. Import GSTR-2B from the portal and reconcile.
5. Fix any 2B mismatches (book missing purchases, chase suppliers who haven’t filed).
6. Prepare GSTR-3B after 2B is clean.
7. Pay the net tax on the portal.
8. File both returns and mark them filed in Booksmor with the ARN.

Each step is below in detail.

Step 1 — Prepare GSTR-1

GSTR-1 is your monthly statement of every outward supply (sale).

1. Set Return period to the month you’re filing (e.g. 2026-04).
2. In the GSTR-1 (outward supplies) card, click Prepare.

Booksmor reads every posted sales voucher and credit note for the period and assembles the return — split into:

• B2B (sales to GST-registered customers)
• B2C-Large (interstate sales above ₹2.5 lakh to consumers)
• B2C-Small (other consumer sales)
• Exports
• Credit notes
• HSN-wise summary
• Documents issued summary

The card now shows a summary table of each section’s counts and totals. Click Download JSON to save the GSTN-format JSON file you’ll upload to the portal (or hand to your CA).

Filing — two paths

Path A — via the portal (most users):

1. Download JSON from Booksmor.
2. Upload it to the GST portal (gst.gov.in) using the offline tool or the portal’s bulk upload.
3. File on the portal; copy the ARN it issues.
4. Back in Booksmor, paste the ARN into the ARN from GST portal (offline) field and click Mark filed (offline).

Path B — via Booksmor’s GSP (when connected):

1. Click File. Booksmor hands off to the GSP, which submits to GSTN and returns the ARN.
2. The card flips to ”✓ Filed — ARN …” and the period locks (you can’t edit historical vouchers for this period after filing).

Once filed, GSTR-1 locks the period for sales corrections — any change has to route through a Credit Note or Debit Note (per GSTN rules).

Step 2 — Preview GSTR-3B

3B is the summary return where you pay the net tax (output minus input credit).

1. In the GSTR-3B (net tax) card, click Preview.

Booksmor shows the 3B summary table:

• Total output tax (CGST, SGST, IGST split)
• Total input tax credit (matched against vouchers + 2B)
• Net tax payable
• Reverse charge supplies
• Late fee / interest (if applicable)

Preview is read-only — useful for cash-flow planning (“I owe ₹47,000 next week”).

Step 3 — Import & reconcile GSTR-2B

GSTR-2B is the auto-generated statement from GSTN showing every invoice your suppliers declared against your GSTIN. Reconciling this is the #1 way to avoid losing input credit — if a supplier didn’t file or filed wrong, you can chase them before claiming credit you might lose.

1. Download GSTR-2B from the GST portal (Returns Dashboard → 2B → Download).
2. Either upload the JSON, or convert it to CSV with header supplier_gstin,invoice_no,taxable,tax_amount.
3. In the GSTR-2B reconciliation card, paste the CSV into the textarea.
4. Click Import & reconcile.

Booksmor compares each 2B row to your purchase vouchers and shows a status for each:

Fix mismatches before preparing 3B so your input credit number is accurate.

Step 4 — Prepare GSTR-3B and file

After 2B is clean, return to the GSTR-3B (net tax) card and click Prepare.

The flow from here mirrors GSTR-1:

• Download JSON to upload to the portal yourself, or
• File through the connected GSP.

After filing, paste the ARN into the ARN field and Mark filed (offline). The period locks for purchases too.

ITC register and RCM

The ITC register & RCM card shows the period’s eligible input tax credit (from purchases) and any reverse-charge supplies you’ve self-accounted for (e.g. legal services, GTA freight where the recipient pays GST).

• ITC register — every purchase with GST that contributes input credit, grouped by tax bucket.
• RCM (reverse charge — supplies you self-account) — vouchers where you’ve booked the GST instead of the supplier. Tagged via the supplier’s RCM flag at the time of posting.

Both feed into the 3B preview automatically; the card is for your own verification.

e-Invoice and e-Way bill

When is e-Invoice required?

Under current Indian GST rules, businesses above a turnover threshold (currently ₹5 crore aggregate annual turnover, may change) must generate an IRN (Invoice Reference Number) from the NIC portal for every B2B sales invoice. If your turnover is below the threshold, e-invoice is optional.

Generating IRN

In the e-Invoice & e-Way bill (posted sales) card, you’ll see each posted sales / credit note voucher with two buttons:

• IRN — submits the voucher to the NIC portal (via GSP) and returns an IRN.
• e-Way — generates an e-Way bill for the goods movement (required above ₹50,000 / state-dependent).

The result appears in the rightmost column: “IRN abc123…” or “EWB 4571…”.

Manual IRN (offline path)

If you’ve generated the IRN yourself on einvoice.gst.gov.in:

1. Paste the IRN into the Manual IRN box for that voucher.
2. Click Add.

Booksmor stores the IRN against the voucher so it shows on PDFs and prints.

TDS / TCS register

A small register at the bottom of the page for tracking TDS/TCS withheld on specific transactions (e.g. 1% TDS on payments to contractors under section 194C).

• Kind: TDS or TCS
• Section: e.g. 194H (commission), 194C (contractor)
• Base + Rate % — Booksmor calculates the withholding amount.

Click Load to see what’s already on file; Add to record a new entry.

For payroll TDS (salary), use the dedicated Payroll → Tax (TDS) module instead. That one computes monthly TDS from each employee’s annual gross + declarations and routes to the 24Q quarterly filing.

QRMP — quarterly filers

If your turnover is below ₹5 crore, you can opt for QRMP (Quarterly Return, Monthly Payment) — file GSTR-1 and 3B quarterly but pay tax monthly via a self-assessed challan.

In Booksmor:

• Tick QRMP (quarterly) in Settings → GST.
• Use period strings like Q1-2026 (Apr–Jun), Q2-2026 (Jul–Sep), etc. in the GST page’s Return period field.
• Each quarter’s GSTR-1 and 3B work the same — Booksmor just aggregates three months’ vouchers.

The monthly tax payments themselves are done outside Booksmor (on the GST portal); Booksmor records the resulting payment via a Journal voucher when you’re done.

Common questions

My turnover is small. Do I need to file every month? GST registration triggers monthly returns regardless of turnover. The only relief is QRMP (quarterly returns + monthly payments) for those below ₹5 crore — tick it in Settings.

My CA does the filings. Do I still need this page? Yes — to prepare the returns (which compile data from your vouchers), download JSONs, and reconcile 2B. The actual upload + ARN comes from your CA’s portal session; bring it back here and Mark filed (offline) to lock the period.

Why does Booksmor lock the period after filing? GSTR-1 once filed is GSTN-immutable. Any change to a B2B invoice must route through a Credit/Debit Note, not an edit to the original. Locking prevents accidental edits that wouldn’t reach GSTN.

Can I file last month’s return if I’m already in next month? Yes — set Return period to the past month and prepare/file. There’s no deadline enforcement in Booksmor; late filing late fees / interest are handled by GSTN on their end.

My GSTR-2B shows invoices from suppliers I don’t recognise. Either you booked the purchase under a different vendor name (and Booksmor’s matcher missed it — manually link the rows), or someone misused your GSTIN. Cross-check with the supplier; if it’s truly bogus, raise a dispute on the portal.

The 3B preview shows a different ITC number than my ITC register. 3B caps ITC to what’s actually claimable per GSTN rules (some ITC is restricted by section 17(5)). The ITC register shows everything in your books; 3B filters by claimability. Cross-check with your CA if the difference is significant.

Booksmor says “GSP simulator” — does that mean my filing is fake? The figures are real (your live vouchers), but the simulator doesn’t push to GSTN — it just returns a mock ARN. Use Download JSON + the portal for the actual filing until a live GSP is connected. When the live GSP goes live on the platform, File will transmit for real.

Can I see the JSON before I download it? Click Download JSON — the file opens in your browser if your OS associates .json with a viewer. Otherwise open it in a text editor.

I added a wrong IRN manually. How do I remove it? Open the voucher (Daily → Transactions, double-click), click Edit, and clear the IRN field. Save. Booksmor doesn’t expose a “delete IRN” button directly — you go through the voucher edit.

Troubleshooting

Prepare button does nothing / “no vouchers for period”. The period has no posted sales (for GSTR-1) or no posted purchases (for 3B input). Check Daily → Transactions to confirm vouchers exist with voucher_date in the period.

GSTR-2B import says “0 rows” or fails. Check the CSV header matches exactly: supplier_gstin,invoice_no,taxable,tax_amount. Header is case-sensitive and column-order-sensitive. Strip any extra columns from your 2B export.

IRN button returns an error. The GSP isn’t connected (simulator mode) — Booksmor returns a mock IRN; if it errored, the simulator itself had a problem. In production, errors usually mean the voucher is missing GSTIN, place-of-supply, or HSN — Booksmor validates these client-side, but borderline cases reach the GSP. Verify the voucher has all required fields.

Mark filed (offline) gives “ARN format invalid”. ARN is a 15-character alphanumeric. Strip whitespace; paste exactly what GSTN gave you.

The 3B preview shows zero output tax even though I have sales. Either GST enabled is off in Settings → GST, or your sales vouchers’ tax rate is 0% per line. Check a few sales vouchers in Transactions; the line GST % should be set.

Need more help? Email support@booksmor.com with: the return period, the JSON file you downloaded (if any), and a screenshot of the error. For GSTN-side issues, your CA is often the faster path.