For most benefits, you must give your national insurance (NI) number when you claim (and your partner’s if you are claiming for them) and enough information to confirm the number is yours. If you don’t know your number, give the DWP sufficient information to allow them to trace it or go to www.gov.uk/lost-national-insurance-number . If you don’t have an NI number, you are still entitled to benefit if you apply for a number and provide enough information and evidence for one to be allocated to you.

You can apply for an NI number online at: www.gov.uk/apply-national-insurance-number . Alternatively, you can contact 0800 141 2079 (textphone 0800 141 2438) or in Northern Ireland 0800 587 0024 (textphone 0800 587 0194). If you are deaf and use British Sign Language, you may be able to apply using a video relay service (see: www.gov.uk/apply-national-insurance-number/how-to-apply).
SSAA , S.1(1A) & (1B)