Construction industry contractors could face huge tax bills dating back more than six years, following a crackdown by the Inland Revenue on bogus self employment. IR is determined to wipe out contractors’ practice of evading tax by classifying workers self employed, despite them effectively being on the payroll full time. It has sent out thousands of letters to contractors and sub contractors, and has warned recipients to take them seriously in light of its plans to increase compliance resources and double its number of site visits. The IR is using “risk profiles”, based on size and geography, to identify sub contractors that are actually employees.