Why this guide?
2025 is shaping up to be the most compliance-heavy year since GST launched. From tighter e-invoicing timelines to “no-edit” GSTR-3B, the accuracy of your GSTR 1 Filing now determines everything from input-tax credit (ITC) flow to penalty exposure. Below is a step-by-step, plain-English roadmap to help you file stress-free—and penalty-free—this year.

1. The Big Picture at a Glance relating to GSTR 1 Filing

Parameter	Rule in force for 2025-26
Who must file?	Every registered taxpayer who makes outward taxable supplies (goods or services), whether B2B, B2C, exports, or zero-rated
Who is not required to file?	1. Composition-scheme taxpayers (file CMP-08 & annual GSTR-4) 2. Input-Service Distributors (file GSTR-6) 3. Non-resident taxable persons (GSTR-5) 4. TDS deductors under §51 (GSTR-7) 5. TCS collectors/e-commerce operators under section 52 (GSTR-8) 6. OIDAR suppliers to unregistered recipients (GSTR-5A)
Periodicity	Monthly if aggregate annual turnover (AATO) in any preceding FY > Rs 5 crore Quarterly (QRMP scheme) if AATO ≤ Rs 5 crore ClearTaxeFiletax
Due dates	Monthly: 11th of the following month Quarterly: 13th of the month after the quarter (use IFF on the 13th of month 2 & 3 to pass ITC to buyers) eFiletax
Nil outward supplies?	File Nil GSTR-1 (portal or SMS) even if there are no sales in the period Pice
Change of frequency	If turnover crosses Rs 5 crore during the current FY, you shift to monthly filing from the next quarter/FY
Hard stop on old returns	From 1 July 2025, any GSTR-1 pending > 3 years from its original due date can no longer be filed on the portal IndiaFilings

New risk areas

• No edits in GSTR-3B Table-3 from July 2025 onwards

• 30-day e-invoice upload rule now extends to AATO ≥ Rs 10 crore from April 1 2025,

Key 2025 change: Returns pending > 3 years become non-fileable after July 1 2025.

2. What’s New in 2025?

1. Tighter GSTR-3B Linkage
2. From the July 2025 period, values auto-pulled from GSTR 1/GSTR 1A will be locked in Table 3 of GSTR-3B. Any corrections will be applied to the brand-new GSTR-1A cycle, potentially delaying buyer ITC if the 14-day window is missed. Accuracy in the first upload is non-negotiable.
3. Mandatory HSN Digits for All
4. The GSTN advisory of January 9 2025, makes a 4-digit HSN compulsory for B2B supplies, regardless of turnover, and a 6-digit HSN if the AATO exceeds Rs 5 crore.
5. Expanded 30-Day e-Invoice Upload Rule
6. AATO taxpayers with a turnover of Rs 10 crore or more must now report every invoice, credit note, and debit note to the IRP within 30 days of issue, effective from 1 April 2025.
7. Faster appeal disposal timelines—missed or incorrect uploads may now escalate more quickly.

3. Step-by-Step Filing Workflow (Portal Method)

1. Reconcile outward supplies in your ERP vs books—preferably by the 5th of every month/quarter.
2. Generate e-invoices & IRN (if under mandate) immediately, ensuring IRN export for GSTR 1 Filing.
3. Use the latest Offline Utility (v.24.12 or later) for bulk upload; it already embeds new HSN validation.
4. Upload JSON → Save → Generate Summary → Preview before submit.
5. File with DSC or EVC and grab the ARN.
6. Download the filed return PDF—your buyer’s ITC hangs on this.

Pro-tip: For QRMP taxpayers, use Invoice Furnishing Facility (IFF) by the 13th of Month 2 & 3 to keep buyers happy.

4. Penalties & Late Fees (2025-26)

Delay (days)Monthly filers, Quarterly filers (per day)

Up to 30 Rs 25 (CGST) + Rs 25 (SGST) Same

Beyond 30 Rs 50 + Rs 50 Same, capped at 0.25% of turnover

Plus, missed e-invoice uploads now carry a Rs 10,000 per invoice penalty (intentional) or Rs 25,000 per invoice for fraud.

5. Common Mistakes to Dodge during GSTR 1 Filing

1. Forgotten B2C (Large) invoices > Rs 2 lakh, skewing state-wise reporting.
2. Negative values in amendments—use absolute figures; the portal automatically reduces.
3. Wrong tax period in e-invoice; IRN date≠and invoice date mismatches freeze ITC.
4. Skipping credit-note linkage—unlinking invites demand notices.
5. HSN/SAC mismatch triggers automated cross-checks with e-way bills from July 2025.

6. Reconciliation Game-Plan

• Sales Register vs GSTR-1 weekly.
• GSTR-1 vs GSTR-3B post-filing.
• GSTR-2B vs Books monthly, escalating discrepancies within 14 days, before the buyer’s ITC cut-off.

7. Top 10 Frequently Asked Questions (FAQs) for GSTR 1 Filing

1. I’m on QRMP; do I still need to upload invoices monthly?

Optional IFF for the first two months; mandatory complete upload in Month 3.

2 . What if I miss the 30-day e-invoice upload?

IRN rejected; invoice considered invalid → No ITC for buyer, potential Rs 10k penalty per invoice.

3 . Can I revise a GSTR 1 after filing?

No “revision” form—use amendments in the next tax period or the new GSTR-1A window (post-July 2025).

4 . How do I correct an HSN error?

Use Table 9C (amended invoices) with the correct HSN; otherwise, risk mismatch notices.

5 Is a B2C (small) summary compulsory?

Yes, Table 7 remains mandatory; otherwise, turnover will be under-reported.

6 Are export invoices zero-rated but reportable?

Absolutely. Report in Table-6A/6B even if tax is 0.

7 Can I file GSTR-1 without DSC?

Firms/companies need DSC; proprietors & LLPs may use EVC linked to Aadhaar.

8 What happens if GSTR-1 & 3B differ?

From July 2025, 3B auto-locks; a different trigger system generated demand for explanation.

9 Returns older than three years—can I still file now?

No. After July 1, 2025, the portal blocks filings beyond a 3-year delay.

10 Do credit notes need e-invoicing?

Yes, if you’re under the e-invoice mandate, the same 30-day IRN rule applies.

8. Final Thoughts

GSTR-1 is no longer just a “statement”; it is the single source of truth driving ITC, analytics, and now even Table 3 of GSTR-3B. Invest in clean data, automate reconciliations, and review every entry twice—a few extra minutes could save months of cash-flow pain.

Need help making sense of all the moving parts? Contact Indefine for hands-on support—from e-invoice integrations to end-to-end filing reviews. Filing right the first time is still cheaper than paying interest, late fees, and audit headaches later.