Since 6 April 2014, with some exceptions, anyone who wants to bring a claim to an employment tribunal must first contact Acas, the advisory and conciliation service. Under section 18A of the Employment Tribunals Act 1996, “the prospective claimant must provide to ACAS prescribed information.” Acas then offers to help reach a settlement “that avoids proceedings being instituted.”
Taking part in conciliation is voluntary. Contacting Acas first is not.