“It’s up to you.”
– we use this to say that the other person can decide something.
1. A: I think I wanna go bowling later. What do you think?
B: It’s up to you. I really don’t mind.
2. A. I want to buy something nice for granny. Do you have any idea what would make a good present?
B. I’m sorry, I suck at giving presents. Can I leave it up to you?