The AC Milan striker said his farewells to his team-mates after training on Thursday after a fee of around £16m was agreed between the clubs.
Balotelli's discipline on and off the field was questioned in his stay with Manchester City from 2010 to 2013 and it was reported later on Thursday that Liverpool were demanding a good behavior clause in his contract.
He scored 17 goals for Milan last season but was booked nine times and sent off once.
Balotelli is reported to be arriving on a private jet later on Friday for a medical but the move will not be completed in time for him to make a debut against his former side on Monday night after the midday deadline passed.
Liverpool have been looking for a striker since the departure of Luis Suarez to Barcelona earlier this summer, although boss Brendan Rodgers previously stated Balotelli was not one of his targets.
Sky Sports pundit Jamie Carragher has mixed feelings about Balotelli's impending arrival at Anfield, telling Sky Sports: "They definitely need a striker, there's no doubt about that.
"At the moment they only have Daniel Sturridge and Rickie Lambert - it looks like Fabio Borini is going to move on - and you need strikers.
"Would he be the final piece of the jigsaw? Would he make the starting XI if everyone was fit and firing? Who knows?
"At the moment Daniel Sturridge has got 36 goals in 50 games for Liverpool and at this moment he is the main man up front.
"Would Brendan then accommodate another striker, whoever that may be, like he did with Luis Suarez?
"He has lots of options now, Brendan Rodgers, and I don't think he will play the same team too often so they do need those options.
"The main thing for any player is what they do on the pitch. Both of those players had issues off the pitch, but I think it's fair to say Suarez did a lot more on the pitch.
"You will always get a little bit more freedom if you're producing on the pitch, that's the main thing for any player.
"Balotelli is a player who has been here before and did a lot of stuff that was good for us in the media. He probably didn't quite show his potential at Manchester City and that, coupled with his off-the field problems, probably saw him depart.
"He's the Italian number one striker and you want to see good players here. Liverpool do need a striker."