These are mostly the same METV requirements when i used to get it a few years ago,
Self assessment - proves you have an income
Employer letter, i was self employed so provided my company reg document.
Pension statement is to show income if now retired, this wasn't specified a few years ago.
School must be if student and going back.
If you haven't got any of those then, maybe they process anyway, or deny, try and see, no refund though