evidence: If an individual’s assets increase in value, that appreciation is income in an economic sense, but the tax code considers it income only when the individual sells the asset and realizes the capital gain as a profit, which is included in taxable income. But when appreciated assets are left to heirs, the unrealized capital gains accumulated up to that point escape the personal income tax forever because of a tax break called the "stepped-up basis."[7] The estate tax is the only tax that might touch these unrealized capital gains on assets left to heirs. [...] The Treasury Department estimates that President Biden’s proposals to close these and other loopholes in the gift and estate taxes would raise $77 billion over 10 years.[8] Sen. Sanders’ estate tax bill also has similar provisions to close these loopholes.[9] [...] [7] Realized capital gains are usually calculated as the profit from selling an asset, meaning the money received for the asset minus the "basis," which is usually the amount paid to purchase the asset. When assets are passed on to heirs, the basis is "stepped up" to the value of the asset when it is inherited. For example, if some asset is originally purchased at a value of $50 million and is then passed to an heir at a current value of $100 million, the heir can immediately sell the asset for $100 million without reporting any capital gain. This rule allows an enormous amount of capital gains to go untaxed.