How do I correct a return if I misunderstood the rules for state estate or inheritance taxes?

The state tax picture can range from estate tax to inheritance tax to no state death tax at all. When preparing the return, the executor and beneficiaries should identify each state with a possible claim and confirm filing thresholds, exemptions, and deadlines before assuming no return is required. For tax reporting purposes, the rule to keep in mind is to separate what happened before death, after death, and after distribution because those dates can move income between different returns. Keep the source paperwork rather than relying only on a summary, and have a CPA, enrolled agent, or tax attorney review who must report it, how basis is determined, which form is used, and when it is due.