Apply to your local council as soon as you need help with rent, because Housing Benefit usually starts from the date you make your claim. You may be able to request backdating if you were entitled earlier and had a good reason for not claiming sooner; the usual maximum is one month for working-age claimants and up to three months for people over State Pension age. Rules and evidence requirements can vary, so check your council’s process and the official GOV.UK guidance. If you rent privately, you may need to claim Universal Credit instead, unless an exception applies.