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Before You File GSTR-1 and GSTR-3B: 20 Easy Checks

GSTR-1 और GSTR-3B भरने से पहले 20 आसान जाँच

A simple tick-list to run every month before filing GSTR-1 and GSTR-3B: sales, GSTINs, HSN, credit notes, IMS, ITC, RCM, reversals and payment, with BUSY steps.

GSTR-1 from BUSY GSTR-3B from BUSY

Most GST notices start with a small slip in GSTR-1 or GSTR-3B: a wrong GSTIN, a missed credit note, ITC taken before the supplier uploaded the bill. Since Table 3.1 of GSTR-3B now comes locked from GSTR-1, a mistake in GSTR-1 flows straight into your tax. Run these checks every month; they take 15 minutes and save weeks of correspondence.

Before GSTR-1 (due 11th, or 13th for QRMP)

#	Check	Why	How (BUSY / tool)
1	Every sale of the month is entered: cash, B2C, exports, SEZ, credit and debit notes	A sale missed now must go through amendment later	Day book / sales register for the month
2	Buyer GSTINs are valid and active	A wrong GSTIN gives credit to someone else and the buyer will chase you	Paste the list into the free GSTIN checker; search doubtful ones on gst.gov.in
3	Bills to registered buyers are B2B, not B2C	B2C hides the buyer's credit	Party master: GST registration type and GSTIN filled
4	Place of supply is right (local = CGST + SGST, other state = IGST)	Wrong tax head means paying again and claiming a refund	Check party state and dispatch details
5	Tax rates on items are current	Rates changed in the 2025 rate rationalisation; old masters cause short or excess tax	Item master: tax category; see change GST rate / HSN in BUSY
6	HSN on every item, with the right digits (4 up to Rs 5 crore turnover, 6 above)	HSN summary (Table 12) is validated by the portal	Item master HSN; HSN summary report
7	E-invoices (IRN) match the books, no cancelled bill left in books	E-invoices auto-fill GSTR-1; a mismatch doubles or drops sales	Compare e-invoice register with sales
8	Credit / debit notes carry the original bill reference	Unlinked notes create mismatches for the buyer	Note voucher: original invoice no. and date
9	Document summary (Table 13): series, from-to numbers, cancelled count	Gaps in series raise questions	Check series in the sales register
10	Last month's mistakes go in amendment tables or GSTR-1A, not as fresh bills	Fresh entries double the sale	Correct in books first, then amend

Before GSTR-3B (due 20th, or 22nd / 24th for QRMP)

#	Check	Why	How (BUSY / tool)
11	GSTR-1 is filed and correct	Table 3.1 is filled from GSTR-1 / 1A and cannot be edited in 3B	Use GSTR-1A for a correction before 3B
12	IMS actions done before the 14th	Only accepted (or deemed accepted) bills reach GSTR-2B	GST portal > IMS
13	Books reconciled with GSTR-2B	ITC only on bills in 2B	Free GSTR-2B matcher, or Bharat GST Champ inside BUSY
14	Blocked credit removed (Section 17(5): food, motor vehicles, personal use, works contract for own building...)	Wrong ITC used must be paid back with 18% interest, plus penalty	Purchase register by account head
15	Reversals: suppliers unpaid over 180 days (Rule 37), exempt / personal share (Rules 42, 43)	Missed reversals come back with interest	Outstanding ageing; 43B(h) checker for MSME suppliers
16	Reverse charge liability included (GTA, legal fees, rent from unregistered persons where notified...)	RCM is paid in cash; ITC only after payment	RCM entry in BUSY
17	Tax payable in 3B = tax in books	Differences show up in GSTR-9 and notices	GSTR-3B vs books
18	Cash ledger has enough balance, ITC set-off order checked (IGST first)	Filing fails or tax is paid twice	Electronic cash and credit ledgers on the portal
19	Interest and late fee, if late	The portal now computes 3B interest itself; check it	Free interest & late fee calculator
20	Save the filed return, challan and working	Needed for audit, GSTR-9 and replies to notices	One folder per month

Three habits that prevent most problems

Enter bills daily, not at month-end: fewer missed bills, fewer wrong dates
Keep party GSTINs and item HSN / rates clean in the masters; one wrong master spoils every bill
Put every due date on your phone: GST & TDS due-date calendar adds them in one click

General information for routine monthly filing; rules, forms and portal steps change often, so check the latest notifications and GSTN advisories. Print this page (Ctrl+P) and keep it as a monthly tick-list.

Need it done for you?

Our team sets this up remotely over UltraViewer, usually the same day. Call or message us, or see BUSY services.

Updated 2026-10-27 · Bharat Busy Care, Authorised BUSY Platinum Partner, Sri Ganganagar

FAQ

What should I check before filing GSTR-1?

That every sale and note is entered, buyer GSTINs are valid, B2B vs B2C and place of supply are right, item rates and HSN are current, e-invoices match the books, and last month's errors go through amendment or GSTR-1A.

What should I check before filing GSTR-3B?

That GSTR-1 is correct (Table 3.1 is locked from it), IMS actions are done, books match GSTR-2B, blocked credit and reversals are removed, RCM is included, tax matches the books and the cash ledger has enough balance.

Can I correct GSTR-1 after filing?

Yes, through GSTR-1A before filing GSTR-3B of that period, or through amendment tables in a later GSTR-1.

Why does GSTR-3B Table 3.1 not let me edit sales?

From the July 2025 period it is filled from GSTR-1 / GSTR-1A and locked. Correct the sales in GSTR-1A first.

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