Confused regarding DBS check

I left my job last December due to complications and was made redundant by the company. I was given a tax code and the p40 however I have not been given a DBS certificate which I am confused about. I was contacted by a recruitment company regarding a administrative position in a children's hospital however the employer is asking for an enhanced DBS certificate from me. I don't know how to get one as I have never had one. From what I understand from checking online is that a DBS check should be carried out by the employer and not the candidate.