The South African Revenue Service (Sars) is digging up the past and imposing sky-high tax assessments on objecting mining companies. Sars first bit Kumba Iron Ore’s Sishen Iron Ore Company, on which it imposed a R5.5-billion assessment. Now the truculent tax terrier has locked its jaws on Exxaro, from which it wants R1.1-billion. Both companies have responded to Sars’ letters of intent, disputing the basis of the proposed adjustments.