many happy returns
I wish you a very happy birthday and many more in the future. Hey Jack, many happy returns! Are you going to do anything special to celebrate the occasion?
many happy returns
Also, many happy returns of the day. Happy birthday and many more of them, as in I came by to wish you many happy returns. This expression was first recorded in a letter of 1779 where the writer meant "Happy New Year," but the present meaning has persisted since the second half of the 1800s.
many happy reˈturns (of the ˈday)
used to wish somebody a happy and pleasant birthday: Here’s your present. Many happy returns!