UK old-fashioned or Indian English做必需做的事
to do what is necessary in a situation
Notify your bank and they will do the needful. 通知你的银行，他们会处理该办的手续。
Kindly do the needful at your earliest convenience.
Please do the needful and take appropriate action.
He had given me firm assurances that he would do the needful.
I suppose there's no sense in putting it off further. Time to do the needful.
See also: needful