If you file GSTR-3B late, the portal now calculates interest for you more fairly. From the January 2026 tax period, interest in Table 5.1 gives you credit for the money already sitting in your Electronic Cash Ledger (ECL), in line with the proviso to Rule 88B(1) of the CGST Rules.
The new formula
Interest = (Net tax liability − minimum cash balance in the ECL from the due date to the date of payment) × (days late ÷ 365) × interest rate
If you had cash in the ECL during the delay, interest is charged only on the shortfall, based on the lowest balance in that period.
When it applies: for a late January 2026 return, the interest is filled into the February 2026 GSTR-3B, and so on for later periods.
Rules for the auto-filled interest
- It can't be reduced. The system-calculated interest in Table 5.1 is non-editable downwards.
- It's the minimum. You must still work out your correct interest and increase the figure if you owe more.
Liability breakup also auto-filled
The Tax Liability Breakup table, which records earlier-period supplies paid in the current return, is filled in from the dates of documents in GSTR-1, GSTR-1A or IFF. The figures are suggestions: you can increase them based on your own records. See it at GSTR-3B → Table 6.1 (Payment of tax) → Tax Liability Breakup, and read our guide on confirming the breakup.
Cancelled registrations: interest via GSTR-10
If your registration is cancelled and your last GSTR-3B was filed late, the interest on that delay is collected through the final return, GSTR-10.
A known glitch
GSTN issued a separate advisory because interest for the February 2026 period was calculated wrongly and filled into the March 2026 GSTR-3B, explaining how to correct it. If those periods apply to you, check the figure.
Tip
Paying tax into the ECL on time, even if you file the return a little late, keeps your interest low under this formula.
