Start by raising the issue in writing with your employer, usually through its HR team or formal grievance procedure, and keep copies of relevant documents. You can contact Acas for free, impartial guidance and, before making most employment tribunal claims, you will normally need to begin Acas Early Conciliation. Tribunal time limits are short and vary depending on whether you are challenging the dismissal, selection process or redundancy pay, so check them promptly. If your employer is insolvent and owes you money, the GOV.UK Redundancy Payments Service may be relevant.