GSTR-3B Filing Guide 2025-26: Due Dates, Tables, & ITC Rules

GSTR-3B is the most critical monthly (or quarterly) summary return under the Indian GST regime. While GSTR-1 is a statement of your outward supplies (sales), GSTR-3B is the return where you calculate your final tax liability, claim your Input Tax Credit (ITC), and actually pay the tax to the government.

Filing GSTR-3B correctly is paramount. A single error in Table 4 (ITC) or Table 3 (Liability) can trigger automated notices (ASMT-10), blocked ITC ledgers, and severe interest penalties calculated at 18% per annum.

This comprehensive guide breaks down the GSTR-3B filing process for the FY 2025-26, highlighting the latest hard-lock restrictions and mandatory reporting rules.

GSTR-3B Due Dates for 2025-26

Filing your return on time is crucial to avoid late fees (up to ₹50/day) and interest.

1. Monthly Filers

Taxpayers with an Annual Aggregate Turnover (AATO) exceeding ₹5 Crores, or those who have opted out of the QRMP scheme, must file monthly.

• Due Date: 20th of the following month. (e.g., April’s return is due by May 20th).

2. Quarterly Filers (QRMP Scheme)

Taxpayers with an AATO up to ₹5 Crores who have opted into the Quarterly Return Monthly Payment (QRMP) scheme file quarterly, staggered by state:

• Category X States (South & West India): 22nd of the month following the quarter.
• Category Y States (North & East India): 24th of the month following the quarter.

(Never miss a deadline. Bookmark our GST Due Dates Calendar to track all upcoming compliance deadlines).

Understanding the GSTR-3B Tables

The GSTR-3B form is divided into highly specific tables. Thanks to system integration, Tables 3.1 (Sales) and Table 4 (ITC) are heavily auto-populated from your GSTR-1 and GSTR-2B.

Table 3.1: Tax on Outward and Reverse Charge Inward Supplies

This is where you declare your tax liability.

• 3.1(a) Outward Taxable Supplies: Your standard B2B and B2C sales. Auto-populated from GSTR-1.
• 3.1(b) Zero Rated Supplies: Exports and SEZ supplies.
• 3.1(c) Nil Rated & Exempt: Goods or services that do not attract GST.
• 3.1(d) Inward Supplies Liable to RCM: Purchases where you must pay the tax under the Reverse Charge Mechanism. (Use our RCM Calculator to compute this accurately).
• 3.1(e) Non-GST Outward Supplies: Petrol, alcohol, etc.

Table 3.2: Interstate Supplies to Unregistered Persons

A breakout of interstate B2C sales, supplies to Composition taxable persons, and UIN holders. This ensures the correct state government receives the IGST revenue.

Table 4: Eligible ITC (The Most Critical Table)

This table dictates how much tax you can offset. The portal auto-populates Table 4(A) exclusively from your GSTR-2B.

• 4(A) ITC Available: ITC on imports, RCM, and all other eligible invoices uploaded by your vendors.
• 4(B) ITC Reversed: You must manually declare ITC reversals here.
  • 4(B)(1): Permanent reversals (e.g., Blocked ITC under Section 17(5) for passenger cars, food & beverages).
  • 4(B)(2): Temporary reversals (e.g., Vendor has not been paid within 180 days).
• 4(C) Net ITC Available: Auto-calculated (4A minus 4B).

Crucial 2025-26 Rule: You cannot claim even ₹1 of ITC if it does not reflect in your GSTR-2B. The portal places a hard lock on ITC claims exceeding the GSTR-2B amount.

Table 5: Exempt, Nil, and Non-GST Inward Supplies

Report purchases that are exempt from GST. While there is no tax implication here, reporting it is mandatory for reconciliation during audits.

Table 6.1: Payment of Tax

This table offsets your gross liability (from Table 3.1) against your Net ITC (from Table 4C).

• The system automatically offsets liabilities using the strict legal hierarchy: IGST credit must be exhausted first before utilizing CGST and SGST credit.
• Any shortfall must be paid in cash via challan.

Common GSTR-3B Mistakes to Avoid in 2026

1. Ignoring RCM Liabilities: Failing to declare RCM liability in Table 3.1(d) and simultaneously claiming it as ITC in Table 4(A)(3). You must pay RCM in cash; it cannot be offset via the ITC ledger.
2. Not Reversing Section 17(5) Blocked Credits: If an ineligible invoice appears in your GSTR-2B, you must actively reverse it in Table 4(B)(1). Leaving it in the Net ITC pool is tax evasion.
3. Mismatches with GSTR-1: Your GSTR-3B liability must perfectly match your GSTR-1 liability. Discrepancies trigger immediate DRC-01B notices demanding the difference.

Conclusion

Filing GSTR-3B is no longer a manual data entry task; it is a reconciliation exercise. Before clicking “Submit”, ensure your books of accounts perfectly match the auto-populated GSTR-1 and GSTR-2B data. To quickly verify your tax math, use our Free GST Calculator before generating your final payment challans.