US citizen on student visa; filing taxes and getting National Insurance number if not working?

Hello, I'm a US citizen in the UK on a student visa. I have not been employed in my time here. Because I have not been employed, I have not received a National Insurance number. My understanding is that I cannot apply for a National Insurance number because I am not working and do not intend to work. I have two questions about this: 1. Do I need to file a tax return? 2. I have a brokerage account at an international brokerage. My brokerage would like me to add my UK tax residency to my account information (my understanding, possibly incorrect, is that because I am residing in the UK, I am a UK tax resident and so should add it). However, to do that, I need to provide my UK tax number. However, as mentioned, I do not have a National Insurance number and as far as I know it is not possible to get one. Is it possible to get some other tax number? Thanks! - Mike

Hi
If you are UK tax resident for the whole tax year, then you are required to declare your world-wide income.  If you have income from outside the UK, then this needs to be declared on a tax return.  If you have no income arising from anywhere in the world, then a tax return is not required.  A self assessment record can be created without the need of a national insurance number.

Thanks! I'm trying to file a self assessment. To do so, I need to register for self assessment. I'm trying to follow the steps at this site: https://www.gov.uk/register-for-self-assessment/y/for-another-reason-for-example-you-have-income-from-a-pension-or-a-property/no-i-m-registering-for-the-first-time However, at a certain point in the workflow, it tells me: "You must have a National Insurance number so we can check your identity." But, I'm not currently working or looking for work (I'm a student). So, when I try to file for a National Insurance number (https://www.apply-national-insurance-number.service.gov.uk/apply/may-not-need-nin) it tells me I'm ineligible. So, how can I register for self assessment?

Hi,
If you are not able to register online you can download the SA1 online from the link below and submit by post with a covering letter to review, 
Register for Self Assessment if you are not self-employed
Thank you.