Gateway account

Hi My mom was trying to file self assessment online but seems like she does not have enough detail to prove her identity. What she got on hand: 1. A non-UK passport 2. a valid address (therefore the post code) 3. UTR 4. information held on credit record She is old already(>70) and not intended to work, thus she doesn't have and did not apply for an NI number. She doesn't have a driving licence too. She has foreign interest income so she needs to file a tax return. Is there any way to submit a tax return with these informations? Or she should apply for an NI number for self assessment purpose? Thank you in advance!

Hi Ellencat305,
Your mother would need to contact our online helpdesk for assistance Technical support with HMRC online services
Thank you.