Jack is a CPA bound by the AICPA's ethical standards, "Statements on Standards for Tax Services." Jack's new client, Susan, has hired Jack to prepare her 2022 tax return. Jack asked for Susan's past 3 years' tax returns upon setting up the engagement. Jack discovered that Susan's 2020 Schedule C business deductions were significantly overstated, causing a NOL that carries forward to 2022. What should Jack do upon discovering the error in the 2020 tax return?