Solomace

Hi all, I was made redundant back in January and when I got my redundancy pay, I wasn’t taxed on £30k, but was taxed on the amount over that. No problem, Today I received a self assessment form and when I've queried on the phone with the HMRC, they said yes I need to fill it in even though I’m not and have never been self employed? I’ve spoken to my colleagues who were made redundant and have similar figures and none of them have been asked to do this, and checking on this website and filling in the self assessment checker, it says I don’t need to. Any ideas on this as to why I’ve got this? No other income, no selling of stuff etc. I did get a new job in March working for another company, but once again not self employed and I’m paying tax as I should on this, Thanks in advance.