How many years? If he thought the RMDs were not taxable from the beginning, that could be as many as 25 years. For omissions of up to 25% of taxable income the statute of limitations on the IRS assessing the additional tax is three years from the regular due date of the tax return or the date of filing, whichever is later. If the omission is more than 25%, the assessment period is six years instead of three years. Filed by the regular due date, a 2019 tax return would be beyond the three-year deadline and a 2016 tax return would be beyond the six-year deadline for the IRS to assess additional taxes.
