Oligarch Act of 2023 This bill imposes a tax on the net value of all taxable assets of a taxpayer as of the last day of any calendar year (wealth tax). The amount of such tax is equal to certain percentages of the net value of all taxable assets of the taxpayers that exceed a specified threshold amount. The bill defines net value of all taxable assets as the excess of the value of all property of the taxpayer, real or personal, tangible or intangible, wherever situated, over any debts (including secured debts) owed by the taxpayer. The definition excludes property with a value of $50,000 or less, tangible personal property, certain property used in a trade or business, or collectibles. The Internal Revenue Service (IRS) must report on the net value of assets subject to the wealth tax within one year after the enactment of this bill and must annually audit not less than 30% of taxpayers required to pay the tax. The IRS may extend payment of the tax for a reasonable period (not to exceed 5 years) for taxpayers with severe liquidity constraints or for whom immediate payment would impose an undue hardship. The bill provides for enhanced penalties for understatements of the value of property subject to the wealth tax.