Tipping is the thorniest subject in dining.
There are no tip monitors to oversee how much you leave your waitperson for his or her service, diligence and attention. There's not even an official rule book on the subject.
Mostly, it's custom and your conscience: You leave what you think is right.
Inevitably, though, your idea of right won't always be the same as someone else's.
Liz Riesberg of Troy, Mich., wrote recently of her tipping experience: At a recent lunch with friends, she said, "I was told you don't tip on the tax — something I've never paid attention to in all the years I've dined out. I give 15 percent to 20 percent of the total — or should I give the tip without the tax added in?"
It wasn't that she wanted an excuse to reduce her tip; she seemed more concerned about the servers.
"These waiters and waitresses don't make a lot of money," she said, and tipping on the pre-tax amount would result in smaller tips for them.
Most Web sites on the subject say it's unnecessary to include tax when figuring the tip — but they also note that most people ignore that and tip on the total, tax and all.
When restaurants calculate tips for large parties, most use the pre-tax amount.
"The guest is paying the tax, and they shouldn't have to tip on that amount," said general manager Tony Amman at No. VI Chop House & Lobster Bar in Novi, Mich.'s Crowne Plaza Hotel. Tipping for service is "a separate issue" from paying tax, he said.
But for many servers, the big issue in tipping now doesn't involve tax.
It's about slower restaurant traffic overall, combined with the effect of coupons and other promotional deals.
Scores of restaurants have cut prices this year through coupons or two-for-one offers. Unfortunately for servers, many diners are tipping on the discounted totals rather than on the regular price of the meal.
That translates into pay cuts for waiters and waitresses, even though they're expected to provide the same level of service as before.
Customers who want to follow accepted tipping conventions should use menu prices, not coupon or two-for-one prices, to calculate their gratuity.
"It should always be done on the original amount, before the discount," Amman confirmed.
So while it's OK to ignore the sales tax when figuring tips, it's not so OK to turn bargain-priced meals into pay cuts for servers.
Distributed by McClatchy-Tribune Information Services.