GSTR-3B filing is the monthly, or quarterly under the QRMP scheme, summary return that every regular GST-registered business must submit, declaring total taxable sales, tax liability, input tax credit (ITC) claimed, and tax actually paid. Unlike GSTR-1, which reports each invoice, GSTR-3B is a self-declared summary that determines how much cash you send to the government for that period. For a small business owner juggling sales, purchases, and working capital, getting GSTR-3B filing right every cycle is what keeps GST compliance clean and avoids interest, late fees, or a mismatch notice later.
This guide walks through what GSTR-3B actually contains, table by table, and gives you a practical, repeatable process for preparing and filing it each period.
What Is GSTR-3B and Who Must File It
GSTR-3B applies to every regular taxpayer registered under GST, including businesses selling through their own website, retail counters, or online marketplaces. It is a summary return, not an invoice-wise one — you report totals for outward supplies, inward supplies liable to reverse charge, ITC claimed, and tax paid, rather than listing individual transactions. Even if you had zero sales and zero purchases in a period, a nil GSTR-3B still needs to be filed; skipping it attracts late fees like any other return.
Businesses under the composition scheme do not file GSTR-3B; they file a different quarterly statement (CMP-08) instead. Regular taxpayers within the government's prescribed turnover limit can generally opt into the QRMP (Quarterly Return Monthly Payment) scheme, which allows quarterly GSTR-3B filing with monthly tax payment through a simple challan. Because eligibility thresholds and due dates are revised periodically, always confirm your applicable scheme and due date on the official GST portal (www.gst.gov.in) before you file.
GSTR-3B Table-by-Table Breakdown
GSTR-3B is organized into numbered tables. Knowing what belongs where makes data preparation far faster.
| Table | What It Captures | Typical Source |
|---|---|---|
| 3.1(a)-(c) | Outward taxable supplies (other than zero-rated, nil, exempt) and taxable value with tax | Sales register / GSTR-1 summary |
| 3.1(d) | Inward supplies liable to reverse charge | Purchase register, RCM tracker |
| 3.1.1 | Supplies made through e-commerce operators where TCS/TDS provisions apply | Marketplace settlement/tax reports |
| 3.2 | Inter-state supplies to unregistered persons, composition dealers, and UIN holders | State-wise B2C summary |
| 4 | Eligible ITC — import, reverse charge, ISD, others; and ITC reversed | GSTR-2B, purchase register |
| 5 | Values of exempt, nil-rated, and non-GST inward supplies | Purchase register |
| 5.1 | Interest and late fee payable, if any | System-calculated / self-assessed |
Step-by-Step Process to File GSTR-3B
Once you understand the tables, filing becomes a routine checklist rather than a scramble at month-end.
- Reconcile your outward supply figures. Pull the same-period sales totals you used (or will use) for GSTR-1 and match them against your sales register or accounting books before entering Table 3.1.
- Pull eligible ITC from GSTR-2B. Table 4 should reflect what your suppliers have actually uploaded and that has flowed into your GSTR-2B for the period, not just what your purchase invoices say you paid.
- Account for reverse charge and import supplies separately. These sit in a different sub-table and are often missed by smaller businesses that only track outward sales closely.
- Compute net tax payable after adjusting eligible ITC against your output liability.
- Set off ITC in the correct order — IGST credit must first be used against IGST liability, then CGST, then SGST, before CGST or SGST credit is applied to their respective liabilities.
- Pay the balance liability through the electronic cash ledger using a challan, then submit and file the return using DSC or EVC.
Documents and Data to Keep Ready
- Sales register or GSTR-1 summary for the period
- GSTR-2B statement (auto-generated on the portal) for ITC figures
- Purchase register, including reverse-charge purchases
- Bank statement or expense records to cross-check that reported purchases match actual payments
- Previous period's electronic cash and credit ledger balances
How OneBooks GST Supports Your GSTR-3B Prep
OneBooks GST does not file GSTR-3B directly, but it removes most of the manual reconciliation that leads to errors in it. When you use GSTR-1 automation to prepare your GSTR-1 from marketplace and direct-invoice data, the same validated B2B, B2C, and HSN summaries in Admin > GSTR-1 Details give you a clean outward-supply figure to cross-check against Table 3.1 before you file GSTR-3B. Admin > Detailed Reports lets you view period-wise summaries across GSTINs, which is useful if you manage more than one registration. The GST calculator is handy for quick tax-rate checks while you review individual line items. Full ledger-based tax computation for GSTR-3B is on our accounting software roadmap, alongside chart of accounts and voucher-level books.
A Practical Example of Computing Net Tax Payable
Numbers make the process concrete. Say a small business has outward taxable supplies of ₹5,00,000 for the month, attracting GST at 18%, giving an output tax liability of ₹90,000. Eligible ITC available in GSTR-2B for the period, after reconciliation, comes to ₹65,000. Net tax payable in cash works out to ₹25,000, split across IGST, CGST, and SGST based on the nature of the supplies and the ITC available in each head. This is the figure that ultimately gets paid through the electronic cash ledger before the return is filed. If your ITC reconciliation is incomplete when you sit down to file, the safer approach is to claim only what GSTR-2B currently supports rather than what your purchase invoices suggest, and pick up any remaining eligible credit once it reflects in a later period's GSTR-2B.
Building a GSTR-3B Filing Calendar
Rather than treating each filing period as a one-off scramble, small businesses that stay consistently compliant usually work off a short internal calendar: reconcile sales a few days after month-end, download GSTR-2B once it is generated, finalize the working sheet, arrange cash ledger funds, and file a day or two before the due date rather than on it. Building this rhythm into your accounting routine reduces the chance of a rushed, error-prone filing and gives you a buffer if a figure needs a second look before submission. It also makes it easier to spot a genuine anomaly, such as a missing marketplace settlement file or an unusually large reverse-charge purchase, while there is still time to investigate it properly.
Amendments Belong in a Later Period, Not the Current One
Because GSTR-3B cannot be revised once filed, any correction you discover after filing — whether it is an understated liability or an ITC claim that needs adjusting — is carried forward and reflected in a subsequent period's return rather than by editing the one already submitted. Keeping a simple log of such adjustments as they come up makes it far easier to explain the numbers if a query arrives later.
Frequently asked questions
Who needs to file GSTR-3B?
Every regular GST-registered taxpayer, including those selling through marketplaces or their own channels, must file GSTR-3B for each return period, even if there were no transactions. Composition taxpayers file CMP-08 instead.
Is GSTR-3B filed monthly or quarterly?
It depends on the scheme you are registered under. Many small businesses within the government's prescribed turnover limit can opt for quarterly filing with monthly tax payment under the QRMP scheme; others file monthly. Confirm your applicable frequency on the GST portal.
Can I file GSTR-3B without filing GSTR-1 first?
The GST system is designed for GSTR-1 (or IFF, for QRMP filers) to be filed before GSTR-3B for the same period, since GSTR-3B's outward supply and ITC figures are meant to align with GSTR-1 and GSTR-2B data.
What happens if I have no sales or purchases in a period?
You still need to file a nil GSTR-3B. Skipping it results in late fees accumulating just like a return with transactions.
Can I revise GSTR-3B after submission?
GSTR-3B cannot be revised once filed. Any correction is made by adjusting the relevant figures in a subsequent period's return, so it is worth reconciling carefully before you submit.
How OneBooks GST handles it
Much of the manual effort above is mechanical, and OneBooks GST keeps imported sales, reviewed output and export files together so the figures behind a GSTR-3B summary stay traceable.
Keeping the original source file, the reviewed working copy and the final export together is what makes the same check repeatable next period, and OneBooks GST stores them against the filing period.
