GST interest under Section 50, calculated

Interest under Section 50 of the CGST Act is 18% per annum on delayed payment of tax and 24% per annum on input tax credit that is wrongly availed and utilised. For a late GSTR-3B, the proviso to Section 50(1) charges interest only on the portion of tax paid in cash, not the part set off by ITC.

The two rates

Section 50(1) levies 18% per annum on tax that is not paid by the due date. Section 50(3), read with Rule 88B, levies 24% per annum on ITC that is wrongly availed and utilised. Credit that is availed but not utilised, and is reversed, generally does not attract interest.

The net-cash relief

The proviso to Section 50(1) is valuable: where a GSTR-3B is filed after the due date (except after commencement of proceedings under Section 73/74), interest is charged only on the tax paid by debiting the electronic cash ledger — that is, the net cash liability after using available ITC. You do not pay interest on the ITC-funded portion.

Example. Output tax Rs.3,00,000; ITC available Rs.2,40,000; net cash Rs.60,000, paid 30 days late. Interest = 60,000 × 18% × 30 ÷ 365 = Rs.888, not on the full Rs.3,00,000.

Circular 192/2023 on ITC interest

Circular 192/2023-GST clarified that for the purpose of Section 50(3), interest on wrongly availed ITC is computed only when the credit is utilised, and the electronic credit ledger balance is examined to see whether the wrong credit was actually used. If the balance always exceeded the wrong credit, no utilisation occurred and interest may not arise. Verify the precise wording for your facts.

Practical computation

Use the GST Interest Calculator for quick figures. For audits, keep a working showing the net cash component for each late period and the credit-ledger movement for any ITC interest, so the computation is defensible.

Worked example: late GSTR-3B

A taxpayer's GSTR-3B for April 2026 (due 20 May 2026) is filed on 18 June 2026 — 29 days late. Output tax is Rs.12,00,000, ITC available in the electronic credit ledger is Rs.7,50,000, so the net cash liability is Rs.4,50,000.

Interest applies only on the cash component because of the proviso to Section 50(1), made retrospective from 1 July 2017 by the Finance Act 2021. Had the entire Rs.12,00,000 been the base, interest would have been Rs.17,162 — the net-cash rule saves Rs.10,726 in this example alone.

When the 18% rate applies on gross, not net

The net-cash benefit is available only where the supplies are declared in a return filed late for the same period. It is not available where liability is determined in proceedings under Section 73 or 74 — in a demand scenario, interest runs on the full shortfall. Similarly, if you declare a past period's supplies in a later month's GSTR-3B, the department's position is that the benefit of netting does not apply to that spill-over liability.

Interest on wrongly availed ITC: Section 50(3)

After the Finance Act 2022 amendment (retrospective from July 2017), interest on wrongly availed ITC applies only when the credit is both availed and utilised, at 18% (the old 24% rate under Section 50(3) was dropped). Rule 88B(3) defines utilisation: credit is treated as utilised only when the electronic credit ledger balance falls below the wrongly availed amount. Practical consequence: if you spot a wrong availment and your credit-ledger balance has never dipped below that amount, reverse it — no interest is payable.

Computation discipline for monthly closes

• Compute interest day-wise from the due date to the date of payment (debit in cash ledger), not month-wise.
• Pay interest through DRC-03 if paying voluntarily after filing, selecting the correct period and Section 50 as the cause.
• GSTR-3B now auto-populates interest via the system-computed Table 5.1 — verify the system figure against your own day-count before filing, especially where liability was spread across tax heads (IGST/CGST/SGST attract separate interest computations).
• Interest is not deductible for income-tax purposes if characterised as penal; interest under Section 50 for delayed payment is compensatory and is generally claimed as a business deduction — document the characterisation.

Use the NumberIQ GST interest calculator for day-count precision, and confirm rates in Notification No. 13/2017-Central Tax (as amended) at cbic.gov.in.

Interest in demand proceedings vs voluntary payment

The timing of payment changes the total cost dramatically because of the penalty ladder in Sections 73 and 74. For a non-fraud shortfall paid before a show-cause notice with interest, no penalty applies under Section 73(5). Paid within 30 days of the SCN, penalty is still nil. After adjudication, penalty is 10% of tax (minimum Rs.10,000). In fraud cases under Section 74 the ladder runs 15% (before SCN), 25% (within 30 days of SCN), 50% (within 30 days of order), and 100% thereafter — but interest under Section 50 runs identically in all scenarios, from the original due date to payment.

Two practice notes. First, interest is self-assessed — Section 75(12) lets the department recover self-assessed interest without any SCN, so an unpaid interest figure sitting in a filed GSTR-3B can go straight to recovery. Second, in a genuine dispute on the principal tax, remember that interest follows tax: winning on the tax demand extinguishes the interest, so do not pay interest "to buy peace" while litigating the tax unless you are consciously settling the period.