The short answer
GSTR-1 is the return where a taxpayer reports the sales they made. GSTR-3B is the summary return where they declare the tax due, claim input tax credit and pay. Monthly filers usually file GSTR-1 by the 11th and GSTR-3B by the 20th of the following month. Because the two returns need different documents on different dates, a CA firm is better off collecting for them as two separate requests.
Due dates can change by government notification, and they differ for quarterly filers, so confirm against the GST portal's calendar before you promise a client a date.
What GSTR-1 covers
GSTR-1 is the statement of outward supplies. It lists the invoices the client issued during the period, along with credit notes, debit notes and amendments to earlier periods. The details flow into the buyers' records, so an error here shows up on other businesses' returns as well.
To prepare it, the firm needs:
- The sales register for the period, or the sales invoices themselves
- Credit and debit notes issued during the period
- Details of exports or supplies to unregistered buyers, where they apply
- Corrections to invoices reported in earlier months
What GSTR-3B covers
GSTR-3B is a summary, not an invoice-level return. The client declares total outward supplies, the input tax credit being claimed and the net tax payable, then pays it. The credit is the part that depends on purchase documents: a claim should be supported by purchase invoices and checked against GSTR-2B, the auto-drafted statement of credit available to the client based on what their suppliers have filed.
To prepare it, the firm needs:
- Sales figures that agree with what was reported in GSTR-1
- Purchase invoices and the purchase register for the period
- Details of any expenses or imports on which credit is claimed
- The bank statement, for clients where the firm also reconciles
Due dates at a glance
- Monthly filers: GSTR-1 by the 11th and GSTR-3B by the 20th of the following month.
- Quarterly filers under the QRMP scheme: GSTR-1 by the 13th of the month after the quarter ends, and GSTR-3B by the 22nd or 24th of that month depending on the state the client is registered in. Tax is paid monthly in between using a challan.
Treat this list as a planning guide, not legal advice. Extensions, waivers and state-wise changes are announced by notification, and the portal calendar or your GST software is the authority.
Why the two returns need separate requests
Asking a client for "GST documents" invites a partial answer. The sales register is easy to find, so that arrives. The purchase invoices and bank statement take more effort, so they wait. By the 18th the firm has half of what it needs for GSTR-3B and a list of people to chase.
A better habit is to ask for each return's documents under its own deadline, by name, for the specific month:
Hello, for August 2026 GSTR-3B we still need: purchase invoices and the bank statement. A photo or PDF on this chat is enough.
A request written like this is finite. The client can see what "done" looks like, and the firm can see exactly what is missing.
A simple collection calendar for a monthly filer
- Early in the month: ask for the sales register and any credit or debit notes. These feed GSTR-1.
- By the 11th: file GSTR-1.
- Mid-month: ask for purchase invoices and, where you reconcile, the bank statement for GSTR-3B.
- By the 20th: file GSTR-3B.
Adjust the timing to your clients. The point is that each request is separate, specific and tied to a date.
Common collection mistakes
- Accepting the wrong month's bank statement because the file looked right.
- Counting the same invoice twice when a client re-sends a photo.
- Treating a verbal "I sent it" as receipt, with no record of what arrived.
- Collecting everything through voice notes and group chats, so nobody can see status at a glance.
How Fyliio handles this
Fyliio starts with GSTR-3B. Staff open a cycle for the month, each client is asked on WhatsApp for exactly the open items on their checklist, and every photo or PDF is matched against that list, with period checks and duplicate detection. Anything uncertain goes to a staff review queue instead of being ticked off automatically. The first request goes out 7 days before the due date, with reminders at 4, 2 and 1 day before, and they stop as soon as the list is complete. GSTR-1, TDS and ITR checklists are planned on the same flow.
Fyliio does not file returns or connect to the GST portal. Your team files in the software it already uses. See how the platform works or the pricing, or read the GSTR-3B checklist clients actually understand.
Frequently asked questions
Is GSTR-3B filed before or after GSTR-1?
For monthly filers, GSTR-1 is due first (the 11th) and GSTR-3B later (the 20th). Filing GSTR-1 first lets you check that the sales in the summary return match the invoice-level return.
Do GSTR-1 and GSTR-3B need the same documents?
They overlap on sales but differ otherwise. GSTR-1 is driven by sales invoices and notes. GSTR-3B also depends on purchase invoices for input tax credit, and on the bank statement where the firm reconciles.
What is GSTR-2B and why does it matter for collection?
GSTR-2B is the statement of input tax credit available to a client, drafted from what their suppliers have reported. Purchase invoices collected from the client are compared against it before credit is claimed.
Can WhatsApp be used to collect these documents?
Yes. Photos and PDFs sent on WhatsApp are enough for most clients, provided each one is matched to a named checklist item and the month is checked. That is the workflow Fyliio automates.
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