IRS Publication 525 Taxable and Nontaxable Income, page 32, outlines different forms of inheritance:
Gifts and Inheritances. In most cases, property you receive as a gift, bequest, or inheritance isn't included in your income. However, if property you receive this way later produces income such as interest, dividends, or rents, that income is taxable to you. If property is given to a trust and the income from it is paid, credited, or distributed to you, that income is also taxable to you. If the gift, bequest, or inheritance is the income from the property, that income is taxable to you.
Inherited Pension or IRA. If you inherited a pension or an IRA, you may have to include part of the inherited amount in your income. See Survivors and Beneficiaries in Pub. 575 if you inherited a pension. See What If You Inherit an IRA? in Pubs. 590-A and 590-B, if you inherited an IRA.
Expected inheritance. If you sell an interest in an expected inheritance from a living person, include the entire amount you receive in gross income on Schedule 1 (Form 1040 or 1040-SR), line 8.
Bequest for services. If you receive cash or other property as a bequest for services you performed while the decedent was alive, the value is taxable compensation.