Maria, a calendar year taxpayer, is audited by the IRS in February 2022 for the tax year 2020. During the course of the audit, the IRS proposes that Maria owes additional taxes because she failed to substantiate certain travel and entertainment expenses. In addition, the IRS discovers that Maria failed to file a tax return for 2015 and, in 2017, an item of gross income amounting to $26,000 was not reported