Most retirement planning focuses on what life looks like when everything goes according to plan. Both spouses are alive.Income is shared.Taxes are filed jointly.Decisions are made together. That is natural. And it makes sense. For years, sometimes decades, that is the reality most couples plan around. What often gets less attention is how the plan changes when life does not stay the same. Not emotionally. But financially. Specifically, how the tax rules shift when a household goes from two...