First, check that you are responsible for a child under 16, or under 20 if they remain in approved education or training. Usually, only one person can claim for each child, and you must be the main person responsible for their care. Your income does not normally prevent a claim, although a High Income Child Benefit Charge may apply if your adjusted net income is over the relevant threshold. Apply through the official GOV.UK Child Benefit service; claims can usually be backdated by up to three months, and claiming may help protect National Insurance credits.