It also shows his national insurance number and appearance bonuses.
A spokesman for the club, said: "We are taking the matter extremely seriously and we are investigating."
The payslip which appeared on a series of football fans' forums, shows he was paid £4,000 in appearance bonuses.
A club insider told the BBC: "It must have been stolen but the player simply doesn't know how it has happened.
"I can assure you that John Arne Riise is not in the habit of throwing payslips out, it's clearly been stolen and taken without his permission."
The Kop hero also landed a Champions League salary increase of £15,384. His take home pay was £82,413 and his monthly tax payment £55,508, while £65 was deducted for meals.
