The remainder of Markovic's economic rights are thought to be owned by an investment fund, as is common in Portuguese football.
Markovic is set to become Brendan Rodgers' fourth signing of the close-season, following deals for Adam Lallana, Emre Can and Rickie Lambert.
The 20-year-old can play in a number of different attacking roles, and Rodgers will hope his arrival at Anfield can help offset the loss of Luis Suarez, who is set to sign a five-year contract with Barcelona this week.
Markovic moved to Benfica from Partizan last June, and played a major role as the Lisbon club completed a domestic treble of Primeira Liga, Taca de Portugal and Taca da Liga.
However, the versatile forward missed Benfica's UEFA Europa League final defeat to Sevilla after being sent off for his involvement in a touchline fracas in their semi-final win over Juventus.
Markovic reportedly passed a medical on Merseyside on Monday, and posted a picture on his official Facebook page holding a Liverpool shirt.
The winger was a reported target for Chelsea prior to his move to Portugal, although a deal failed to materialise.
Benfica have already gone some way to replacing Markovic with the capture of Brazilian teenager Victor Andrade, who moved to the Estadio da Luz on Friday.
Markovic joins a Liverpool side looking to maintain momentum from last season when Rodgers' men saw an unlikely title challenge end in a second-placed finish and UEFA Champions League qualification.
