Different way to say "You are in charge of it now"

Solution 1:

You can use an idiom like "pass the baton" or "take the wheel" or "manage the helm" etc.

Some examples:

As the present great leader of this company, I now pass the baton over to you.

I used to be the boss here, but now I'm asking you to take the wheel.

You're managing the helm now, get to work and keep me apprised!

https://idioms.thefreedictionary.com/pass+the+baton

https://idioms.thefreedictionary.com/take+the+wheel

https://idioms.thefreedictionary.com/helm

Solution 2:

that's your, his, etc. problem / that's (someone's) problem TFD idiom

That is something someone else will have to deal with or figure out; that's not my responsibility or concern.

As in:

What sentence can people use when they hand over a job to someone?

If the job has been a problem, or one has received undue criticism for its management:

That is your problem now!

it’s/they’re ˌall ˈyours another idiom used when passing the responsibility for somebody/something or the use of something to another person:

The job is all yours ... now!

Solution 3:

​ To take control of something, especially an organization or a country, is often known as taking over the reins

Source: Cambridge Dictionary