Barcelona has declined to pay a €26 million bonus that was included in Neymar's contract renewal signed in 2016 after he completed his world-record transfer to Paris Saint-Germain this summer.
Moreover, the Brazilian faces legal action from Barcelona over an alleged breach of contract.
The club said in a statement that the clause relating to the payment was rendered null and void when he left Camp Nou, while agent and father Neymar Sr. has accused Barca of "blackmail".
"It falls on us to explain that the athlete Neymar Junior and his lawyers are aware of the statement released today [for Tuesday] by Barcelona," the statement reads.
"We must emphasise that the news was received with surprise, since the athlete fulfilled the former contract, with the full deposit of the sums freely agreed with Barcelona allowing for his release.
"Nevertheless, when the citation has been read and Barcelona's complaint analysed, the athlete's defence will be present.
"With regards to the bonuses owed from the 2016 contract signing, openly unpaid by Barcelona, it also falls on us to confirm that the athlete has already initiated legal proceedings for collection through the appropriate channels."
The unpaid loyalty bonus is also being investigated by FIFA, although the world governing body has so far declined to comment on the matter.