This Practice Note outlines the UK’s rules to counteract hybrid and other mismatches, also referred to as the anti-hybrid rules. These rules, counteracting deduction/non-inclusion and double deduction mismatches, are found in Part 6A of the Taxation (International and Other Provisions) Act 2010. They replaced the arbitrage (also referred to as the anti-arbitrage) rules with effect from 1 January 2017. This Practice Note was produced in partnership with Dominic Robertson of Slaughter and May.