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by JEANNE FLEMING, PH.D. and LEONARD SCHWARZ

Question: Before my son got married, my wife and I told his fiancée's parents that, in addition to hosting the rehearsal dinner, we'd pay for one-third of the cost of the wedding (we had a general sense of the overall budget). They were very appreciative and agreed to send us an accounting of expenses post-event. Well, we've received it, and it looks to us as if they padded the bill. What should we do?

Answer: Be grateful you didn't offer to pay for half.

Seriously, the first thing to do is everything that discretion allows to determine the actual cost of the event. That means calling all the service providers involved - the caterer, the florist, the band and everyone else - and asking what each of them would charge for a wedding like your son's. In short, nail down the numbers.

Then if they don't add up, say to the bride's parents in your most apologetic voice, "I'm just wondering if there's been some sort of error. We'd been expecting the wedding to cost around [whatever you believe it actually cost]. Could you double-check the math to be certain there's been no mistake?" In other words, without being accusatory, give them a face-saving opportunity to adjust the bill.

And if they don't? While it's perfectly ethical to challenge any bill you believe to be incorrect, you have another obligation here: to support your son's marriage. For the sake of family harmony, hold your nose, write the check and keep your suspicions to yourselves. But never agree to share the cost of anything with these people in the future.

Questions? Email Money Magazine’s ethicists – authors of “Isn’t It Their Turn to Pick Up the Check?” (Free Press) – at FlemingandSchwarz@right-thing.net.