2up is the name of an early payout offer from bookmakers such as Bet365, Paddy Power, Coral, Ladbrokes and Sky Bet. 

If you bet on an eligible match with Bet365 or Paddy Power and your team goes two goals up at any time in the match your bet will be settled as a winner and paid out in cash. If you bet on any match using the special 2UP market for Sky, Ladbrokes or Coral your bet will be paid out in cash if your team goes two goals up at any stage in the match. 

This means that you can make big profits if your team goes two goals up and then does not win the match. This is because both your back bet with the early payout and your lay bet will have won. 

There are other early payout offers on different sports, for example, American football where you are paid out as a winner if your team goes 17 points up at any time. 

To complete these bets you would place a back and lay bet using the standard calculator in normal mode. 

You can find more information about 2up offers here.

You can find a guide on how to use the early payout calculator here.