ANSWER:

No, you’re not sinful if you don’t help him in such frauds and cheating. You must make it clear to him that what he is doing makes his income haram and he is not from the prophet salla Allahu alaihi wa sallam 

QUESTION: I used 2 slaughter goat, only the throat part, in my uncle’s shop. But @ times, wt he does is he takes the goat’s balls and puts it 2 a female goat so tht people wil think it’s male and wil buy it. Or he takes the tail of a goat and attches it 2 a lamb, making it look like a goat so it gets bought. So my QST is am I sinful if I wrk there just 2 cut throat