GST Interest Calculator Tool
How GST interest is calculated (simple formula)
For late filing of GSTR-3B, interest is commonly estimated using:
Days late are counted from the day after the due date up to the payment/filing date. If a due date was extended, use the tool’s manual due-date override.
Why “net cash liability” matters
A common mistake is paying interest on the gross liability even when you have ITC. For many late filing situations, interest is computed on the portion paid via the electronic cash ledger (net cash component) — which aligns with how many taxpayers compute interest after Rule 88B style basis.
Practical outcome
If you have ITC, your net cash liability can be much lower than gross tax — and so can the interest. This tool shows both “gross basis” vs “net basis” so you can see the difference.
Due date helper: Monthly vs QRMP (22nd / 24th)
Use this to pick the right due date assumption quickly — and override it if your period had an extension.
Many taxpayers file monthly. The tool uses a common due-date assumption (typically the 20th of the next month) for estimation.
QRMP due dates are commonly 22nd or 24th depending on the state category. If your due date was extended, use manual override for accuracy.
Due dates may be extended via notifications. If you’re calculating for a month/quarter with an extension, enter the actual due date in the tool.
Examples
These examples show why net cash liability matters. You can replicate them in the tool in under 30 seconds.
- Net cash liability = ₹20,000
- Interest ≈ 20,000 × 18% × 10/365
- Gross-basis interest would be ~5× higher
- Net cash liability = ₹50,000
- Interest ≈ 50,000 × 18% × 30/365
- Use manual due-date override if extended
Common mistakes to avoid
These are the mistakes that typically inflate interest estimates or give the wrong day count.
If ITC is available, interest is often computed on the net cash component. This tool shows both so you can compare.
Month/quarter due dates can vary. If the due date was extended, use manual due-date override — it changes “days late” directly.
Days late depend on the date you actually paid/filed. Use the correct date consistently (and ensure time zone isn’t shifting date inputs).
Wrong ITC utilised (Section 50(3)) follows a different timeline (utilisation → reversal/payment). This tool focuses on late filing interest (50(1)).
Frequently asked questions
What interest rate applies for delayed GST payment/late GSTR-3B filing?
For late payment/late filing related interest under Section 50(1), the commonly applied rate is 18% per annum for the delay period (subject to the facts and applicable provisions).
How are “days late” counted?
Days are counted from the day after the due date up to the payment/filing date. If the due date was extended via notification, use the manual due-date override for accurate day count.
What if my ITC is higher than gross liability?
Net cash liability becomes ₹0 (interest on net cash basis becomes ₹0). But always confirm whether your ITC is actually eligible/available for that period on the portal.
What if I paid tax on time but filed late (or vice versa)?
Interest depends on the specific facts (when liability was discharged and when it became due). Use the payment/filing date you’re modelling and verify with portal computation or professional advice for edge cases.
Is interest calculated on gross liability or net cash liability (Rule 88B concept)?
For many late filing/late payment scenarios, interest is commonly computed on the portion paid through the electronic cash ledger (net cash component). This tool estimates interest using net cash liability (gross minus eligible ITC).
What due date does the tool assume for Monthly vs QRMP?
Monthly mode uses a common default due date (typically 20th of next month). QRMP mode uses 22nd or 24th based on the selected category. If your actual due date differs, use manual override.
Does this tool calculate interest for wrongful ITC utilised (Section 50(3))?
Not in this version. Wrong ITC utilised cases follow a different timeline (utilisation → reversal/payment) and need a dedicated “Section 50(3)” mode/tool.
What should I do after calculating interest?
If you’re late, also check late fee exposure and upcoming due dates: use the GST Late Fee Calculator and the GST Calendar. Keep a record of the due date you relied on (especially if extended).
Accuracy & sources
This tool is meant for estimation and planning. Due dates can be extended, and special situations (e.g., proceedings / notices) may change computation basis. Use manual due-date override for extensions and verify applicable notifications and portal computation for your case.
- Late filing interest estimate (Section 50(1)) at 18% p.a.
- Net cash liability basis (gross minus ITC) for estimation
- Monthly vs QRMP due-date helper + manual due-date override
- Share/export actions (copy summary, PNG, print)
- Wrong ITC utilised (Section 50(3)) advanced timeline calculations
- Case-specific computations during proceedings / adjudication
- Notification-specific exceptions beyond manual due-date override
Related GST Tools
Useful next steps if you’re filing returns or estimating penalties/credits.