GSTR-3B Filing Guide Feb 2026: Interest Calculation & New Rules
You can file GSTR-3B every month or quarter to report your sales, claim tax credits, and show your payments. If you are filing GSTR-3B in February 2026, you will notice a major change. The GST portal now has an automated system that calculates interest on late payments. These interest amounts are already filled in Table 5.1, so it is important to know how the system tracks your payments.
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What changed in the interest calculation in 2026
Previously, many people calculated interest on the full tax payable amount or used rough estimates. The portal now uses a revised formula aligned with the rules and focuses on the cash shortfall rather than the full tax liability.
Revised interest formula
Interest = (Net Tax Liability minus Minimum Cash Balance in ECL from due date to date of debit) × (days delayed ÷ 365) × applicable interest rate
What this means for your business?
If you had already deposited some money in your Electronic Cash Ledger on or before the due date, then interest should apply only on the remaining cash shortfall. The money already available on time should not incur interest.
Book A Demo
Where you will see this new interest calculator in GSTR 3B
- Open your GSTR 3B for the return period.
- Go to Table 5.1. The portal auto-populates the interest there.
- That interest value cannot be reduced inside the return.
Sometimes, interest from a previous period may appear when you file your next return. This can make it seem as if the interest appears unexpectedly.
Let’s understand this with the help of examples.
Example 1: You deposited partial cash before the due date
- Net tax liability to be paid in cash: Rs. 1,00,000
- Cash already available in Electronic Cash Ledger on due date: Rs. 40,000
- Remaining cash deposited later: Rs. 60,000
- Delay: 13 days
- Interest rate: 18%
Interest is calculated only on Rs. 60,000 because that was the cash shortfall after the due date.
Interest = 60,000 × 18% × 13 ÷ 365 = 384.65
Example 2: You had enough cash before the due date, but filed late
If your full cash required for payment was already deposited in your Electronic Cash Ledger on or before the due date, then the shortfall is zero. In such cases, interest should not apply to that portion even if you file the return late. The new portal logic is designed to reflect this benefit through the minimum cash balance concept.
Note: You cannot reduce the interest amount calculated by the system. You can only increase the value if your own records show you owe more.
The other GSTR 3B changes were launched with the interest calculator
1) Auto population of past period tax liability breakup
If you’re paying tax now for supplies from an earlier period, the portal can fill in the Tax Liability Breakup Table for you, using document dates from GSTR 1, GSTR 1A, or IFF. This makes period-wise reporting clearer.
2) ITC utilisation becomes more flexible after IGST ITC is exhausted
After you use all your IGST ITC, the portal allows you to use CGST and SGST ITC to pay IGST in any order in Table 6.1.
3) Cancelled GSTIN case
If your registration is cancelled and you file the last GSTR 3B late, the interest for that delay can be collected through GSTR 10.
GSTR-3B Due Dates & Late Fee (2026)
Here is the current filing schedule:
1. GSTR-3B Filing Deadlines
| Regular (Turnover > ₹5 Cr) | Monthly | 20th of the next month |
| QRMP Scheme | Quarterly | 22nd or 24th of the month after the quarter |
2. Late Fees vs. Interest
Most people worry about the ₹50/day fee, but in 2026, the Maximum Cap, based on your turnover, is what matters. If you're late, you won't pay infinite fees; they stop at these levels:
Daily Rates
- Nil Return: ₹20 per day (₹10 CGST + ₹10 SGST)
- Taxable Return: ₹50 per day (₹25 CGST + ₹25 SGST)
The 2026 Maximum Caps (Per Return)
| Annual Aggregate Turnover | Nil Return | Maximum Cap |
|---|---|---|
| Up to ₹1.5 Crore | ₹500 | ₹2,000 |
| ₹1.5 Crore to ₹5 Crore | ₹500 | ₹5,000 |
| Above ₹5 Crore | ₹500 | ₹10,000 |
The 3-Year Hard Stop
Starting in 2026, the GST portal has introduced a 3-year filing limit. If you miss a GSTR-3B return for more than three years from its original due date, the portal will block you from filing it entirely. You essentially lose the right to ever fix that period, which can trigger heavy departmental scrutiny.
How to file GSTR 3B after the Changes
Step 1: Plan your cash deposit before the due date
If you expect any reconciliation delays, deposit cash into the Electronic Cash Ledger before the due date. As the new rule, this can reduce interest because the minimum cash balance is counted.
Step 2: Reconcile before you open GSTR 3B
- Match outward supplies with GSTR 1
- Match ITC with GSTR 2B
- Check reverse charge entries.
Step 3: Check the auto sections first
- Check Table 5.1 for system-computed interest.
- Check the Tax Liability Breakup Table if you are paying for invoices from older periods now.
- Check Table 6.1, set off sequence, and Input Tax Credit utilisation flexibility.
Step 4: Pay and file
Complete the payment set off, preview your return, submit it, and then file using DSC or EVC.
Conclusion
The 2026 GSTR 3B updates are more than just visual changes. The interest calculator automatically computes interest, which is charged only on the cash shortfall after the due date, not on your full tax amount. So, if you deposit cash before the due date, you can lower your interest, even if you file a bit late.
