Mark Hancock is a self-employed attorney who operates his law practice as an unincor- porated sole proprietorship. In 2017, the IRS disallowed several business deductions he took in 2015 and 2016. In addition to paying the deficiency and assessed penalties, he also pays $18,000 in interest on the tax owed. Can he deduct that interest in the current year? Sec. 162, Sec. 163 Reg. Sec. 1.163-9T Kikalos v. Comm., 84 AFTR 2d 99-5933