In the United States, assets left to a spouse or any qualified charity are not subject to U.S. Federal estate tax. Assets left to any other heir, including the decedent's children, may be taxed if that portion of the estate has a value in excess of the estate tax exemption. As of 2018, the federal estate tax exemption was $11,180,000. For a married couple, the combined exemption is $22,360,000.
Next, start adding your non-tangible assets to your list, such as things you own on paper or other entitlements that are predicated on your death. Items listed here would include brokerage accounts, 401(k) plans, IRAs, bank accounts, life insurance policies, and other policies such as long-term care, homeowners, auto, disability, and health insurance.