Mistakenly signed up for self assessment

I signed up for self assesment thinking I was going to receive some taxable income. This isn't going to happen now. I've just received my letter with my UTR, does this mean I will know have to complete a self assesment? as I don't have any need to PAYE covers all my income.

Hi David,
You will not need to complete a Self Assessment return, but you will need to let us know that you no longer have to - you can do this via:
Self Assessment tax returns.
Thank you.