Barcelona will have to pay an extra 100 million euros (£89 million) on top of any transfer fee if they try to sign another Liverpool player before 2020.
BBC Sport understands the deal was struck as part of Brazil playmaker Philippe Coutinho's £142 million move to Barcelona in January.
Coutinho, 26, joined former Liverpool striker Luis Suarez at the Nou Camp.
Spanish media reports the deal for the extra transfer charge was agreed for three seasons.
According to The Times, the deal was brokered by Liverpool's sporting director Michael Edwards.
Suarez made the switch from Anfield to the Nou Camp in 2014 in a £75m transfer, joining former Liverpool midfielder Javier Mascherano, who moved in 2010 for £17.25m.
Barcelona originally wanted to sign Coutinho in August 2017 following the departure of Neymar to Paris St-Germain, but were forced to wait until January after Liverpool initially refused to let the Brazilian leave.
Coutinho has five goals in all competitions for Barcelona this season.
LM10BARCA10
223
Barca buy every Liverpool player every four years macherano 2010 Suarez 2014 Coutinho 2018 2022???
Dannydrexx
208
That deal was meant to tell barca ..."you have taken enough do not come asking again"
whykallar
173
Well my Barca enjoy shopping at Liverpool, we always offer them best prices and they got lot of profits from our three transactions, but right now they worry we might come for Mane or Sslah 😀 We always buying good and long lasting products ftom them ...
Nigeria5950943
133
Barcelona fc's director of football right now.. It seems our player shopping mall has been closed.
CHERIF10
131
LIVERPOOL.... don't worry Barca coming back for another hunting ..... Naby Keita, Firmino are next in line
Gautam Ranjan
88
Probably had no idea about this...thanks all football