Free tools
Useful Before You Ever Sign Up
Small tools for jobs every firm does each week. They read the same rule tables as OneTrails, show the rule behind every figure and need no account.
- GST
GST Due-Date Calendar
Every GST return date for a state and filing type, with an iCal feed for your phone.
Open the tool - GST and TDS
Late Fee and Interest Calculator
What a late GSTR-3B, GSTR-1 or TDS return costs, worked out from the rule tables.
Open the tool - TDS
TDS Rate Finder
The section and rate for a payment, under the Income-tax Act 1961 and the 2025 Act side by side.
Open the tool - GST
GSTIN Validator
Checks the format and check character of a GSTIN and reads out its state and PAN.
Open the tool - GST
HSN and SAC Lookup
Search by words or code and see the GST rate in force today, with its notification.
Open the tool
How Far to Trust the Numbers
Every date, rate and fee on these pages comes from the OneTrails rule tables, with the date each rule took effect and whether it is verified, known or still uncertain. They are not tax advice: check the figure on the government portal before you file or pay.