Learn what GSTR-1 and GSTR-3B each do, the order to file them in, and a week-by-week monthly routine that keeps GST filing from becoming a month-end scramble.
For most small businesses in India, GST filing is not difficult in the way tax law is difficult. It becomes difficult because of when the work happens. Invoices are raised through the month on a bill book, in a spreadsheet, or over WhatsApp. On the 8th of the following month somebody sits down to assemble all of it, discovers three bills with no GSTIN and two jobs that were never invoiced at all, and spends two days reconstructing a month that has already ended.
The people who feel this most are the owner of a 10 to 40 person business and whoever handles accounts part-time alongside another role. The cost is not only their time. Late filing carries a fee and interest. Invoices left out of GSTR-1 block a customer's input tax credit, which turns into a payment dispute. And a filing backlog eventually stops goods moving, because the e-way bill portal blocks generation for businesses with returns outstanding beyond a set period.
This article covers what each of the two monthly returns actually does, the order they have to be done in, a week-by-week routine that spreads the work across the month, and the specific mistakes that cause most reconciliation problems.
GSTR-1 reports the outward supplies you made during the period. B2B invoices go in individually, with the customer's GSTIN, invoice number, date, taxable value and tax. B2C sales are reported in summary. Credit notes and debit notes issued during the period go in too, as do amendments to invoices reported in earlier periods.
You are not paying anything when you file GSTR-1. You are making a declaration, and that declaration has a direct consequence for someone else: your B2B customer's input tax credit comes from what you report here. An invoice you leave out is credit your customer cannot claim.
GSTR-3B is a summary return. It totals your output tax for the period, sets your eligible input tax credit against it, and leaves a net figure that you pay in cash through the electronic cash ledger. The return will not submit until that payment is made, so there is no such thing as filing GSTR-3B and paying later.
Most of GSTR-3B is auto-populated from two sources: your own GSTR-1 for the outward side, and GSTR-2B for the credit side. That auto-population is the reason the sequence matters.
GSTR-2B is an auto-drafted statement of the input tax credit available to you, built from what your suppliers reported in their returns. It is static: once generated for a period, it does not change. Credit that appears in it is credit you can substantiate. Credit that does not appear in it is credit you will be asked about.
GSTR-2B is generated after the deadline for suppliers to file has passed, which is why purchase reconciliation cannot be done in the first week of the month. This single fact sets the shape of the entire monthly routine.
Before building a routine, establish which of the two filing schedules you are on, because the dates differ substantially.
QRMP reduces filing work. It does not reduce payment work, and it delays credit for your B2B customers by up to a quarter unless you use the optional Invoice Furnishing Facility to upload B2B invoices in the first two months. A business selling mainly to other businesses generally has an easier time on the monthly schedule, because the alternative generates customer phone calls.
Take a small electrical contracting firm on monthly filing. In one month it raises 22 invoices: 18 to businesses and 4 to individual homeowners. It also buys materials from four suppliers and pays for a rented vehicle.
In GSTR-1, the 18 B2B invoices are reported individually with each customer's GSTIN. The 4 homeowner invoices are reported as a B2C summary. One invoice from the previous month, raised with a wrong GSTIN, is corrected through an amendment.
After the 14th, GSTR-2B arrives showing credit from only three of the four material suppliers. The fourth has not filed. That supplier's tax, say ₹18,000, is not available as credit this month. If the firm claims it anyway, its GSTR-3B will not agree with its GSTR-2B, and the burden of explaining the difference sits with the firm rather than with the supplier who caused it. If the firm instead calls the supplier on the 15th, there is a reasonable chance the credit appears next month with nothing else required.
The vehicle rental is a separate question: whether credit is available on it depends on the nature of the supply and how the vehicle is used, which is exactly the kind of item worth confirming with an adviser once and then applying consistently.
The sequence below assumes monthly filing. QRMP filers run the same steps on a quarterly cycle, with a monthly payment step added.
Every invoice should be created when the sale happens, not reconstructed later. This is the step that determines how hard the rest of the month is. An invoice raised at the customer's site from a phone, or at the counter at the moment of billing, carries the correct date, the correct customer and the correct tax rate. An invoice typed up three days later from a note carries whatever the person typing it remembers.
Confirm three things. Every invoice for the period is recorded. Every return, cancellation or price correction has a credit note against it. Nothing is sitting completed but unbilled. Then validate the GSTINs on B2B invoices — a single wrong character puts an invoice in the wrong party's statement, and correcting it requires an amendment in a later period.
Reconcile before submitting, not after. The figures to check are total taxable value and total tax, split by rate, against your own sales register. If those totals agree, the line-level detail almost always agrees too. If they do not, find the difference now — an error in GSTR-1 flows straight into GSTR-3B.
Download GSTR-2B and compare it line by line with your purchase register. Three categories of difference come out, and each needs a different response.
If the first three steps were done, this is a review rather than data entry. Check the auto-populated output tax against your GSTR-1, check the credit figures against your reconciled 2B position, reverse any credit you are not entitled to, and pay the net liability.
Keep a running list of anything unresolved — suppliers who have not filed, credit under query, amendments pending. Reviewing it quarterly is what stops a small unresolved item becoming a year-end write-off.
Cash sales in a notebook, a job invoiced over WhatsApp, an advance received and never converted into an invoice. Each one is a difference at reconciliation, and collectively they are the single largest source of GST filing pain in small businesses.
Tempting when a supplier is slow. It moves the problem from your supplier's compliance to your own, and it is the difference most likely to be picked up.
A return or a rate correction that never became a credit note leaves your output tax overstated for that period, which means you have paid tax you did not owe. Recovering it later is more work than issuing the note at the time.
It is possible, and it means typing figures the portal would have populated. The two returns then disagree, and you have created a reconciliation item for no reason.
A wrong GSTIN found on the 10th is a rushed correction. The same error found when the invoice is raised is a five-second fix, and validating the number against the customer master at that moment is what makes the difference.
Two missed months is an administrative problem. Six is an operational one, because unfiled returns eventually block e-way bill generation and stop deliveries. See our guide to when you need an e-way bill for how that block presents itself at the loading bay.
Every failure mode above is a data-entry gap rather than a gap in tax knowledge. The businesses that file calmly are the ones where an invoice is created once, at the moment of the sale, and never re-entered anywhere else.
VeloCrew handles GST invoicing and the underlying accounts in one system, so a bill raised in the field or at a counter is already in the ledger the GSTR-1 summary comes from. Purchases recorded against suppliers are there when GSTR-2B arrives, which turns reconciliation into a comparison rather than a rebuild. For service businesses raising invoices at the customer's site, the related mechanics are covered in GST invoicing for service businesses.
The practical recommendation is narrow: fix the invoicing moment, then follow the sequence. Raise invoices as sales happen, close sales in the first five days, file GSTR-1 by the 10th, reconcile against GSTR-2B after the 14th, and file GSTR-3B by the 20th. Almost every filing problem a small business has is caused by doing one of those steps out of order or too late.
General guidance only, not professional advice. Rules change — confirm the current requirements for your business with a qualified professional.
GSTR-1 is a statement of your outward supplies. You list the invoices you raised, and no tax is paid when you file it. GSTR-3B is the summary return where you declare total output tax, set off input tax credit against it, and pay the balance in cash. GSTR-1 feeds your customers' credit; GSTR-3B settles your own liability.
GSTR-1, always. Most of GSTR-3B is auto-populated from the GSTR-1 you filed for the same period, so filing GSTR-3B first means keying figures by hand that the portal would have filled in, and creating a mismatch you then have to explain.
As a practical matter, credit not reflected in GSTR-2B is credit you will be asked to justify. The safer route is to treat a missing entry as a supplier problem and chase the supplier to file or correct their return, rather than claiming it and carrying the exposure yourself. Speak to your tax adviser about any specific case.
Two charges apply. A late fee accrues for each day of delay per return, at a lower rate for nil returns and subject to a cap, and interest runs on any tax paid after the due date. Beyond the money, returns file in sequence, so one missed month blocks the next and a long backlog can eventually block e-way bill generation.
It is easier for filing and no easier for your customers. Under QRMP you file returns quarterly but still pay tax monthly, and your B2B buyers wait for their credit unless you upload invoices monthly through the Invoice Furnishing Facility. If most of your sales are B2B, monthly filing usually causes fewer disputes.
There is a statutory cut-off tied to the returns of the following financial year, not an open-ended window. This is why credit discovered during a year-end audit is often discovered too late to claim. Reconciling monthly is what prevents it.
Explore how VeloCrew can help you manage employees, field operations, attendance, tasks, HR and business workflows from one login — built for Indian operations teams. Every account starts on a 14-day Pro trial.
Start free ›Prefer a walkthrough first? Request a demo for your business.