You haven't returned your XX yet. When do you plan on returning it?
You were supposed to return the XX by today. When do you think you can return it?
この場合、次のような言い方ができますよ。
ーYou haven't returned your XX yet. When do you plan on returning it?
「まだXXwo返却されていませんが、いつ返却ご予定ですか？」
ーYou were supposed to return the XX by today. When do you think you can return it?
「今日までにXXを返却されることになっていますが、いつ返却できますか？」
to return で「返却する」
ご参考まで！
カナダ 
