If you pay your restaurant bills with with a credit card, there's a small chance a crooked waiter will jack up the tip by scribbling the amount you added. If you don't go over your receipts and compare them to your credit card statement each month, you'll never know if you've been a victim of this form of fraud.
I know for a fact this has happened to me at least once. I had a meal at Mexicali Concina Cantina in Studio City, CA. I paid with a credit card and left a cash tip. When I got my credit card statement, I happened to have the receipt handy, and I discovered that I had been overcharged by exactly ten dollars. I called my credit card company, and they reversed the charge.
Punny Money has a way to help you catch tip fraud without having to compare your receipts to your statements (you do need to save your receipts, though). You use a checksum method. Adjust the pennies in your tip so the last digit to the right of the decimal point equals the sum of the digits to the left of the decimal point of the total bill.
When you get your statement, the fraudulent tips are easy to spot: