GST tools that actually do the math
No sign-up, no spreadsheet. Free calculators and checkers grounded in current GST rules — a taste of the intelligence inside GST365.
Late-fee & interest calculator
See exactly what a delayed GSTR-3B or GSTR-1 will cost — late fee (with the correct cap) plus 18% interest.
Estimate only. Late fee is split equally as CGST + SGST. Interest runs on net cash tax at 18% p.a. (Section 50).
Due-date finder
Enter your state and filing scheme to get your GST calendar — monthly vs QRMP, and the 22nd vs 24th split.
QRMP is available up to ₹5 crore turnover. Dates shift for holidays and government extensions.
GSTIN verifier
Validate any 15-digit GSTIN — format, state, PAN and checksum — instantly, right in your browser.
Validation is 100% in your browser (format + state + checksum). It does not confirm the GSTIN is active on the portal.
Which plan fits me?
Answer three quick questions and we'll recommend the GST365 plan that matches how you file.
Answer the three questions and we'll match you to the right GST365 plan.
These calculators are free tools for quick estimates, grounded in current GST rules (late fees, caps and 18% interest as researched in 2025). They're informational, not a filing — verify with a professional before you act.
✦ GST — advisory to answer
Like the tools? The platform is the real thing.
These free calculators run on a fraction of GST365's engine. Get the full advisory, reconciliation and notice-response suite.
No credit card required · Free plan for 1 GSTIN · Windows & macOS