You should apply for Universal Credit as soon as you become eligible, because your claim normally starts on the date you submit it online. You can ask for the claim to be backdated by up to one month, but this is only allowed in certain circumstances and the Department for Work and Pensions (DWP) must accept your reason. Request backdating through your online application or journal and explain why you could not claim earlier. Check the latest rules on GOV.UK or contact the Universal Credit helpline if you are unsure.