The Auditor
Enter your receipt numbers and the printed suggested tip. We recompute the math both ways and issue a verdict.
Press Audit to see the worked arithmetic.
Where the Money Goes
Live proportions of subtotal, tax, and tip from your audit inputs.
Quick Tip Calculator
Presets, custom percent, and rounding options.
Bill Splitter
Split the all-in total evenly, then nudge individual shares.
Why Receipts Inflate Suggested Tips
Many point-of-sale systems compute suggested gratuity on the post-tax total rather than the pre-tax subtotal. On a $204.01 subtotal with 9% tax ($18.36), a 20% tip on the post-tax total is 222.37 × 0.20 = 44.47, versus 204.01 × 0.20 = 40.80 pre-tax — a $3.67 difference on one dinner. If you eat out twice a week at that check size, that quiet markup costs roughly 3.67 × 104 = $381.68 per year. Etiquette guides generally say tipping on the pre-tax subtotal is perfectly proper; the tax is not a service.
FAQ
Should tip be on pre-tax or post-tax?
Convention and most etiquette authorities say the pre-tax subtotal is the correct base. Tipping on the post-tax total is generous but not required.
Why does the printed suggestion not match my math?
Usually the system used the post-tax total, included fees, or applied a percentage to a discounted item at full price. The Auditor above tells you which.
Is a small rounding difference an error?
Differences under a couple of cents are normal rounding. The Auditor treats anything within 2 cents of a correct base as a match.