Slaughter and May has advised on a landmark ruling that will see hundreds of companies receive millions in compensation from HM Revenue & Customs (HMRC). Following a 12-year battle, the House of Lords ruled that companies wrongly charged advance corporation tax (ACT) should be able to recover interest on the sums on a compound interest rate rather than a lower flat rate. Claimant Sempra Metals will be entitled to claim compound interests on payments of ACT between 1974 and 1998. The test case paves the way for hundreds of companies in the ACT Group Litigation Order to move their claims forward. Sempra instructed Slaughters dispute resolution partner Sarah Lee and was represented by lead counsel Laurence Rabinowitz QC of One Essex Court. Ian Glick QC, also of One Essex, acted for HMRC.