The Brazil international directly communicated this desire to the Merseysiders via email on Friday following a strong statement from Fenway Sports Group (FSG) that his exit would not be sanctioned this summer.
Barca saw two bids swiftly batted away for the 25-year-old, the last of which was tabled in midweek and totalled €100 million.
Both proposals were accompanied with the message that he was not on the market at any price, a stance repeated on several occasions by Jurgen Klopp.
It was furthered with FSG's definitive position that "no offers for Philippe will be considered and he will remain a member of Liverpool football club when the summer window closes".
In response to that move from the owners, sporting director Michael Edwards was notified of the playmaker's intentions in the afternoon.
Liverpool had not originally expected Coutinho to agitate to leave given the player's own wish to move to Camp Nou only if a deal could be agreed on amicable terms.
However, by lunch time on the eve of the club’s season opener at Watford, they were anticipating his request with some media outlets reporting he had already sent it through.
The Reds are not shifting from their position and insist they will turn down further approaches from Barca.
"If FSG is saying something like this, then that’s the statement," Klopp noted in his pre-match media briefing.
"I’ve said it already a few times, but maybe it’s not been 100% clear, but now you can read it - maybe that’s the difference!
"That’s the way it will go and there’s nothing else to say about this."
Coutinho will not be available for selection at Vicarage Road due to a back injury, which will also make him a doubt for the first leg of the Champions League play-off against Hoffenheim on Tuesday.
He signed a new five-year deal without a release clause in January, which has emboldened Liverpool's attitude towards the situation.