How GSTR-3B Auto-Interest Now Works in Table 5.1 (Jan 2026)

Key Takeaways

• From the January 2026 tax period onwards, interest in Table 5.1 of GSTR-3B is auto-populated by the GST portal using the proviso to Rule 88B(1) of the CGST Rules, and it cannot be reduced below the portal figure.
• Interest is charged only on the net shortfall in your Electronic Cash Ledger (ECL) between the due date and the date you actually offset the liability, not on gross tax liability.
• The system-computed figure is the minimum interest payable. Taxpayers can revise it upward but cannot reduce it below the portal value.
• The rate is 18 percent per annum under Section 50(1) of the CGST Act, 2017 (Notification 13/2017-Central Tax).
• If you filed a late GSTR-3B for the January 2026 period, the auto-calculated interest shows up in the February 2026 GSTR-3B in Table 5.1.

Many businesses now open GSTR-3B and see a pre-filled interest figure in Table 5.1 that they cannot lower. This follows the GSTN advisory of 30 January 2026 on interest collection and related enhancements in GSTR-3B, updated on 19 February 2026. This guide explains exactly what changed, how the interest formula works, and what to do when the auto-populated figure does not match your own working.

What Changed in January 2026?

The law itself did not change in 2026. Since 1 July 2017 (by the retrospective proviso to Section 50(1), inserted by the Finance Act 2021), interest on a delayed return is payable only on the tax paid in cash. Since 5 July 2022, Rule 88B(1) (inserted by Notification 14/2022-Central Tax) also spells out that any amount already credited to the Electronic Cash Ledger by the due date, and not debited until the return is filed, is excluded from interest.

What changed is the portal. Before the January 2026 tax period, Table 5.1 showed a system-suggested interest figure that taxpayers could edit, including downward. From the January 2026 tax period onwards, the GST portal computes interest after giving the benefit of the minimum cash balance available in the ECL from the due date till the date of offset, and that figure becomes the floor.

The first live impact was visible in the February 2026 GSTR-3B, which carried auto-populated interest for any delayed return of the January 2026 period.

The Interest Formula

The portal computation follows this logic:

Interest = (Net tax liability payable in cash for the period minus Minimum cash balance available in the ECL from the due date to the date of debit) × (Number of days of delay / 365) × 18%

Three things to notice:

1. Cash portion only. The base is the part of your liability you pay in cash, after ITC is applied. Interest does not apply on the ITC-offset portion of a delayed return.
2. Minimum ECL balance gives relief. If money was already sitting in the ECL from the due date, the portal treats it as partial discharge. You pay interest only on the gap.
3. 18 percent per annum under Section 50(1). The rate is unchanged. Only the way the portal applies it has changed.

Worked Example

A Hyderabad trading company has a cash liability of Rs 4,00,000 for the January 2026 GSTR-3B. The due date is 20 February 2026. The return is actually filed on 10 March 2026, which is 18 days late (21 to 28 February is 8 days, plus 1 to 10 March is 10 days). The Electronic Cash Ledger had at least Rs 1,50,000 throughout, from 20 February to 10 March.

Under the portal formula:

• Net shortfall = Rs 4,00,000 minus Rs 1,50,000 = Rs 2,50,000
• Interest = Rs 2,50,000 × 18 / 100 × 18 / 365 = Rs 2,219

Computing interest on the full Rs 4,00,000 would give Rs 3,551. The portal figure is Rs 2,219 because the Rs 1,50,000 sat untouched in the ECL for the whole delay. A late fee of Rs 50 per day for 18 days (Rs 900) is payable separately.

Table 5.1 is Now "Editable Upward Only"

This is the behaviour that most taxpayers miss on their first filing after the change.

• The portal-computed figure is the minimum interest payable for that period.
• You can increase the figure if your own computation gives a higher amount.
• You cannot reduce the figure below what the system has computed, even if your internal working produces a lower number.

If you believe the portal figure is wrong because the ECL history has been misread, keep your working and raise a grievance through the GST portal helpdesk. Do not expect to override Table 5.1 downward during filing.

Why Many Businesses See "Unexpected" Interest in Their GSTR-3B

Three situations cause the pre-filled number to differ from what finance teams expect:

1. Interest from an earlier period appears in a later return. Interest on a delayed January 2026 return shows up in the February 2026 GSTR-3B, because that is the next return filed after the delayed payment. Teams that look only at the current period's liability and ignore the Table 5.1 figure get surprised.

2. Finance team calculated on gross liability. Some older ERP set-ups still compute interest on the full output tax before ITC offset. For a delayed return the portal charges it only on the cash shortfall, so the internal figure is often higher than the portal figure.

3. ECL was used during the delay window. The portal looks at the minimum cash balance across the whole delay period. If the balance was used on day 3 and topped up on day 10, the minimum between due date and offset may be zero, and interest will be charged on the full cash liability.

What You Should Do Before Filing the Next GSTR-3B

1. Open Table 5.1 before you submit. Do not rely on your offline working. The portal figure is now a floor.
2. Reconcile the ECL movement. Download the Electronic Cash Ledger statement from the due date through the payment date. The minimum balance during that window is what the portal used.
3. Keep a working paper. Save a screenshot of Table 5.1 and the ECL statement together. If a notice comes later, this is your evidence of how the interest was determined.
4. Do not try to override downward. Pay the system figure and raise a grievance if you genuinely disagree.
5. Review your cash management policy. Because the portal gives credit for the minimum ECL balance during a delay, depositing cash through PMT-06 by the due date can meaningfully reduce interest if you expect a late filing.

How This Connects to Other GSTR-3B Portal Changes

The auto-interest mechanism is one of several portal changes that move GSTR-3B figures from self-entry to system computation. The verified ones are:

• Table 3 liability in GSTR-3B is auto-populated from GSTR-1/GSTR-1A/IFF and non-editable from the July 2025 tax period (GSTN advisory of 7 June 2025). No GSTN advisory or CBIC notification locks ITC in Table 4 or imposes a "zero mismatch" block; see why GSTR-3B filing can get blocked for what the portal actually validates.
• Returns cannot be filed after three years from their due date (Sections 37(5), 39(11), 44(2) and 52(14), inserted by the Finance Act 2023), enforced on the portal from the July 2025 tax period. See the three-year filing cutoff.

Finance teams that keep their ECL and filing calendar clean will see the smallest interest bills.

Let Tax Garden Handle the Interest Reconciliation

Reading Table 5.1 correctly, matching it to the ECL movement, and keeping the supporting papers is slow work to do alone every month. Tax Garden runs the reconciliation for you, flags the exact reason for any auto-populated interest, and files GSTR-3B so late filings happen only when they have to. See our GST return filing service or talk to our team.

Frequently Asked Questions

Can I reduce the auto-populated interest in GSTR-3B Table 5.1 if my own working is lower?

No. From the January 2026 tax period, the portal figure in Table 5.1 is treated as the minimum interest payable, so you can only increase it (GSTN advisory of 30 January 2026, updated 19 February 2026). If you think the system misread your Electronic Cash Ledger history, keep your ledger statement and working and raise a grievance on the GST portal helpdesk rather than expecting to edit the table downward.

Is GST interest charged on the full tax liability or only the cash portion?

For a delayed return, interest under Section 50(1) of the CGST Act is 18% per annum on the part of the liability discharged in cash, after input tax credit is set off (proviso to Section 50(1), effective retrospectively from 1 July 2017). This does not apply if the return is filed after proceedings under Section 73 or 74 have started. Rule 88B(1) further excludes any amount that stayed in your Electronic Cash Ledger from the due date until the date of debit, so only the net shortfall attracts interest.

Why does interest for one month show up in the next month's GSTR-3B?

The portal computes interest after a delayed return is actually filed and the cash is debited. So interest for a late January 2026 return is auto-populated in Table 5.1 of the next GSTR-3B filed, which is the February 2026 return. Finance teams that check only the current period's liability are often surprised by this carry-forward figure.

How can I reduce interest if I know my GSTR-3B will be filed late?

Deposit the expected cash liability into the Electronic Cash Ledger by the due date using a PMT-06 challan and leave it there until the return is filed. Because interest is charged only on the gap between your cash liability and the minimum ledger balance during the delay, money kept untouched in the ledger from the due date cuts the interest. Using that balance for something else during the window lowers the minimum balance and so raises the interest.

What is the late fee for filing GSTR-3B after the due date?

Separately from interest, a late fee of Rs 50 per day (Rs 25 CGST plus Rs 25 SGST) applies for a delayed GSTR-3B, or Rs 20 per day for a nil return. It is capped by Notification 19/2021-Central Tax at Rs 500 for nil returns, Rs 2,000 for turnover up to Rs 1.5 crore, Rs 5,000 for Rs 1.5 crore to Rs 5 crore and Rs 10,000 above Rs 5 crore (CGST plus SGST combined). The portal computes it when you file the delayed return and it must be paid in cash, not from input tax credit.