# GST Interest Calculator: 18% on Late Tax, Section 50 > GST interest calculator under section 50: interest at 18% a year on tax paid late in cash or on ITC wrongly used, day by day, with the per-day cost. Source: https://trykosh.com/tools/gst-interest-calculator Free tool - Business and GST # GST interest calculator under section 50 Work out the interest you owe when GST is paid after the due date, or when input tax credit was wrongly claimed and used. Interest runs day by day at 18% a year. Rules checked 25 October 2026Free - no sign-upRuns in your browser Interest payable INR 2,138 51 days at 18% a year on INR 85,000 Per day**INR 41.92** Days**51** Tax + interest**INR 87,138** Tax paid late (cash portion) INR 85,000 Rate 18% a year 20 Aug 2026 to 10 Oct 2026 51 days INR 85,000 x 18% x 51 / 365 INR 2,137.81 Interest payable INR 2,138 Interest is charged only on the tax you pay in cash, because ITC already in your ledger counts as paid on time. It must be paid in cash. ## Upload your statement and Kosh does this for you. Upload your bank statements and Kosh separates business from personal spending and keeps your tax and GST dates in view. [Start free](/signup?via=tool-gst-interest-calculator) ## How the GST interest calculator works Under section 50(1) of the CGST Act, tax paid after its due date carries interest at 18% a year, counted for each day from the day after the due date until the day you pay. Since September 2020 (with effect back to July 2017), interest is charged only on the part of the tax paid in cash, that is, your liability after setting off input tax credit, as long as the return is filed before any proceedings begin. Under section 50(3), interest applies to input tax credit that was wrongly availed and also utilised. The Act allows a rate of up to 24%, but the notified rate has been 18% since July 2017 (Notification 09/2022-Central Tax). Credit that was wrongly claimed but never used carries no interest: it counts as utilised only when the balance in your credit ledger falls below the wrong amount. Enter the amount, the date interest starts (the return due date, or the date the wrong credit was used) and the date you paid or reversed it. The calculator applies amount x rate x days / 365. The rate is editable in case an order applies something different. Interest has to be paid in cash through the electronic cash ledger, usually in the same GSTR-3B where you pay the delayed tax. Unpaid interest can be recovered like tax, so it's worth clearing it in the next return. Interest = amount x 18% x days / 365 amount net tax paid in cash late, or ITC wrongly availed and utilised days from the day after the due date to the date of payment ## Worked example: Kiran, electronics trader in Coimbatore, pays July's GST late Kiran's GSTR-3B for July 2026 showed INR 2,40,000 payable in cash after using his credit. It was due on 20 August 2026 but a customer's payment came in late and he paid on 28 September, 39 days later. Interest is INR 2,40,000 x 18% x 39 / 365 = INR 4,615.89, so about INR 118 for every day of delay. He pays INR 4,616 in cash with the return. Interest payable INR 4,616 39 days at 18% a year on INR 2,40,000 Per day**INR 118.36** Days**39** Tax + interest**INR 2,44,616** Tax paid late (cash portion) INR 2,40,000 Rate 18% a year 20 Aug 2026 to 28 Sep 2026 39 days INR 2,40,000 x 18% x 39 / 365 INR 4,615.89 Interest payable INR 4,616 Interest is charged only on the tax you pay in cash, because ITC already in your ledger counts as paid on time. It must be paid in cash. [Load this example into the calculator ->](?amount=240000&to=2026-09-28#calculator) ## Good to know - Interest is on the net cash liability only if you file the return before a notice. Tax demanded after proceedings start carries interest on the gross amount. - The GST portal pre-fills interest in GSTR-3B for the previous period's delay; check it against your own figure rather than paying blindly. - Reversing wrongly claimed credit before using it avoids interest altogether. Reconcile your purchase register with GSTR-2B every month. - Interest on late GST is compensatory, so it is generally allowed as a business expense for income tax. Penalties are not. Confirm the treatment with your accountant. ## Frequently asked questions What is the interest rate on late GST payment? 18% a year, charged per day under section 50(1) of the CGST Act. It applies from the day after the due date to the day of payment, on the tax paid in cash. Is GST interest 24% for excess ITC claims? The Act sets 24% as the upper limit for interest on input tax credit wrongly availed and utilised, but the government notified 18% with effect from 1 July 2017. So in practice both late tax and wrongly used credit attract 18%. Is interest charged on the gross GST liability or the net? On the net amount paid in cash, after setting off input tax credit, provided the return is filed before any proceedings. Credit already in your ledger on the due date is treated as tax paid on time. Can GST interest be paid from the credit ledger? No. Interest, late fee and penalty must all be paid in cash from the electronic cash ledger. ## Sources and assumptions - [CBIC GST portal](https://cbic-gst.gov.in/) - [GST Council](https://gstcouncil.gov.in/) Rules and rates last checked on 25 October 2026. Results are estimates for planning and education, not tax, legal or investment advice. Kosh is an educational financial planning tool by Primedepth Labs. It is not a SEBI-registered investment adviser and does not offer personalised investment advice, hold your money or execute trades. Markets carry risk; read scheme documents carefully and consult a registered adviser before acting.