The IRS properly issued a supplemental assessment seeking a repayment of an employment tax refund it accidentally issued to a Seattle landscape architecture firm because the original assessment was imperfect, the US Tax Court said Wednesday. Two years after the IRS mistakenly assessed a $0 federal employment tax liability on Hough Beck & Baird Inc.'s first quarter of 2021 and issued a $121,000 refund, the agency sent a letter proposing an adjustment of the same amount.