Losing a spouse can be devastating, and survivors often face a costly surprise — higher future taxes . But couples can plan ahead to reduce the burden, experts say. The issue, known as the "survivor's penalty," happens when shifting from married filing jointly to single filer, which can lead to higher tax rates, depending on the couple. Single filers have less generous tax brackets, a smaller standard deduction and lower thresholds for other tax breaks. It's one of the "most overlooked and