Should I have told the CSA I was working?

I have unwitingly made a bad mistake with the csa and not informed them im working.

I’m self employed and my daughter left school two years ago. I didnt know i had to inform them that i was working because my daughter had left school and was working, i have arears which i know i have to pay, they now want to speak to me about comitting fraud for not informing them im working.

I really dont know which way to turn on this matter and badly need advice? does anyone know of where i gofrom hear and where i stand legally?