Q: When I sold my condo last spring, the homeowners association billed the escrow for my share of painting the building. Now the association says it made a mistake, and I owe $750 more. Am I obliged to pay this?

A: "Hang on, you owe us more money": That's got to be one of the most unwelcome phrases in the English language.

If you knew the original bill was wrong, you should have pointed out the error then, and you should pay the correct amount now. Otherwise, talk to a lawyer about where you stand legally. But ethically speaking, you're not obligated to pay up. Organizations with bookkeepers and accountants are responsible for getting their bills right. Your former homeowners association knows that in real estate, closing means closing and escrows don't have do-overs. So that $750 shortfall is their problem, not yours.

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.