GST ReconciliationPractical GST Tools & Knowledge
GST TOOL • GSTR-3B

GSTR-3B Interest Calculator

Select the tax period and State, enter only the tax actually paid through the Electronic Cash Ledger under IGST, CGST and SGST/UTGST, and enter the actual filing date. The calculator determines the applicable return due date from the filing pattern and applies recorded due-date extensions in its rule set.

1. Select return period

Interest is calculated only for the delay period after the applicable due date, using the actual filing date.

2. Cash tax paid

For January 2026 onward, GSTN enhanced GSTR-3B interest computation to consider the minimum Electronic Cash Ledger balance available from the due date until tax payment. Enter it only when you have reliable ledger data.

Interest result

0Interest days
18%Normal annual rate
₹0Cash tax base
₹0Estimated interest
Tax headCash taxECL benefit appliedInterest baseInterest
Legal basis: Section 50(1) of the CGST Act provides interest for delayed payment of tax; section 50(2) provides that interest is calculated from the day succeeding the day on which tax was due. Rule 88B prescribes the manner of calculation, including the net tax liability/cash-ledger treatment for delayed filing situations.

Official basis checked against GST/CBIC material: Section 50 of the CGST Act; Rule 88B of the CGST Rules; GSTN's January 2026 advisory on enhanced GSTR-3B interest computation; GSTN QRMP due-date guidance. This calculator is an estimate and should be reconciled with the GST Portal's system-calculated interest before payment.

How the due date is determined

For monthly filers, the normal GSTR-3B due date is the 20th of the succeeding month, subject to government extensions. For QRMP quarterly filers, the GST Portal's guidance provides the 22nd/24th state-group due-date structure. The calculator uses the State only when the selected filing frequency is quarterly.

Government notifications can change a due date or provide special relief for a specified class, tax period or State. The calculator therefore contains an internal extension/relaxation rule table and displays the rule applied in the result instead of asking the user to manually enter the due date.