New U.K. tax rules are being introduced from April 2020 to make businesses liable for determining the employment tax status of contractors who work through personal service companies (“P.S.C.’s”). These outsourcing arrangements have had a devastating effect on tax collections and funding for National Insurance, the U.K. version of Social Security. The goal of the new rules is to make customers of P.S.C.’s liable for collecting wage withholding tax and National Insurance contributions that are not collected by the P.S.C. when the worker of the P.S.C. would otherwise be properly characterized for U.K. tax purposes as an employee of the customer of the P.S.C. under tests published by H.M.R.C. Any company involved in the P.S.C. arrangement may have inchoate liability for payments of wage withholding tax and National Insurance. Penny Simmons, of Pinsent Masons LLP, London, explains the scope of the exposure and expounds on procedures that should be adopted in advance of the April 2020 effective date.