why is it not venitul anual tau? Is it because it is the genitive form and if so, would my translation also be correct?
You could say "care este venitul anual al tau?" and it would be correct.
Im not sure if it is because of the genitive form, but i can assure you that the correct translation you wanted to go for is "venitul tău anual". But you were close enough! :))
Think of it like "what is (care este) the income that belongs to you (îți)", and then change a bit the order (care îți este / care-ți este )
That makes the most sense. Thanks!