Despite “strong evidence” of negligence, a state appeals court held yesterday that an attorney representing the seller in a real estate transaction did not commit legal malpractice because his former clients failed to show that deficiencies in his performance cost them a $5.1 million tax break.

In scrutinizing a 2007 deal for the $10.2 million sale of 496 Broadway in Manhattan, a 4-1 majority of the Appellate Division, First Department, faulted Howard Stern of White Plains for telling his clients he was not qualified to handle the tax arrangement they had in mind, but nonetheless represented them in the transaction.