You can ask your local council to backdate Council Tax Support, but the rules and maximum period depend on its scheme and whether you are of working or pension age. You will usually need to explain why you did not claim sooner and provide evidence of your income, circumstances and the date you believe support should start. Backdating is not automatic, and the council decides whether your reasons and evidence meet its rules. Check your council’s Council Tax Support page for deadlines and appeal or reconsideration steps if your request is refused.