A cash inheritance is not taxable on your federal return. The IRS doesn't impose an inheritance tax.
Only the distributions from an inherited traditional IRA are taxable, just as they are for non-inherited traditional IRAs. Distributions from an inherited Roth are not taxable unless the Roth was established within the past 5 years.
Only a handful of states (Iowa, Kentucky, Maryland, Nebraska, New Jersey and Pennsylvania) have some kind of inheritance tax. Refer to your state's Department of Revenue to see what the requirements are for filing inheritance tax.
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