Free GST tools
Three small tools that run in your browser. There is no sign-up, and nothing you type is sent to us.
GST calculator
Add GST to an amount, or take it out of a price that already includes it. Shows CGST and SGST, or IGST.
GSTIN validator
Check that a GSTIN is built correctly: its length, its state code and its check digit.
GST return due dates
The next due dates for GSTR-1, GSTR-3B and other common returns, for monthly, quarterly and composition filers.
These tools follow the rules as we last checked them on 12 November 2026. Rates and dates can change. Verify on the GST portal before you act on a result.
Want the bills to do this for you?
SG Works ERP works out the tax on every invoice and prepares your GST figures from your bills. We reply within 24 hours on business days.