Volunteering and on Social Welfare

My sister has just recently opened up her own business. I have been helping her with it but she is not paying me so I am still claiming Social Welfare. I am actively looking for work and my sister knows that this is only a temporary thing. My question is do I need to inform the Social Welfare Office of this.

I would imagine so. It's probably easier to tell them upfront rather than try and explain things if someone reports you.