Reverse Sales Tax Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026
Disclaimer: This calculator is provided for informational and educational purposes only and does not constitute financial, medical, legal, or other professional advice. Always consult a qualified professional before making decisions based on these results.
Working backward from a receipt total
Sometimes only the final tax-inclusive total is known - a receipt or invoice showing just the amount charged - and the pre-tax amount needs to be separated out for accurate expense recording or reporting purposes.
Worked example
For a $107 total charge at a 7% sales tax rate:
Pre-Tax Amount = 107 / (1 + 7/100) = 100.0 pre-tax (7.0 tax)
This example was deliberately chosen to land on clean numbers ($100 pre-tax plus exactly $7 tax) to make the reverse calculation easy to verify - the same formula works for any total and tax rate combination.