The IRS provided additional guidance on the 0.9% additional Medicare payroll tax by updating two frequently asked questions (FAQs) on its webpage addressing the situation in which an employer under- or overwithholds the tax in one year and discovers the error in a subsequent year. Updated FAQs No. 56 and No. 57 say that, while the employer may not correct the error by making an interest-free adjustment, it can correct the amount of wages and tips subject to the withholding on the appropriate adjusted withholding return.