1. The four most common bill tricks
Most overcharges are not typos — they are design choices. Once you know the patterns, each one takes seconds to spot.
- Suggested tip calculated on the after-tax total. A 20% tip quoted on a bill that includes 9% tax is really a ~21.8% tip on the pre-tax food.
- Automatic gratuity or service charge added, with the suggested tip line still printed. You end up double-tipping if you follow both.
- Itemized totals that do not add up — line items totaling more than the printed subtotal.
- Round-up or “convenience” fees placed in fine print at the bottom of the receipt.
2. The math behind an inflated suggestion
Here is how a “20% suggestion” becomes 22%. Say your food comes to $82.57 and tax is $7.43, making the total $90.00. A terminal that calculates 20% on the total suggests $18.00. But 20% of your actual pre-tax spend is $16.51 — the printed suggestion is 21.8% of the food, a hidden 1.8-point markup.
That gap grows with the tax rate. In Chicago (10.25%) or Seattle (10.35%), a “20%” suggestion computed on the total is effectively 22%+. On a $200 dinner that is roughly $4–5 you never agreed to.
3. How to check a bill in 30 seconds
Look at three numbers only: the pre-tax subtotal, the tax, and the total. Verify that subtotal + tax + your tip equals the total before you sign. Then compute the suggested tip as a percentage of the pre-tax amount — not the total — to see if it is fair.
4. When a service charge is (and is not) a tip
A mandatory “service charge” or “gratuity” on a group of 6+ is legally a tip in most U.S. states and usually goes to staff. An itemized “service fee” added by the restaurant may go to the owner instead — that is a hidden fee, and you are not required to tip on top of it by default.