Everton target Allan does not have a release clause in his contract at Napoli.
The Brazilian midfielder could move on from Napoli in the summer transfer window and Everton boss Carlo Ancelotti is an admirer of his talents, having coached him in Italy.
It has been claimed in some quarters that Allan has a release clause in his Napoli contract but, according to Sky Italia, that is not the case.
Allan's contract contains no release clause, placing Napoli in a strong position to dictate the terms of his departure.
Allan has attracted interest from a number of teams and it remains to be seen how many go in with formal offers to Napoli for his services.
The 29-year-old still has another three years left to run on his contract at Napoli.
He has now made over 200 appearances for the club since joining and featured regularly under Ancelotti earlier this season.
Allan has also turned out in all but one of Napoli's Champions League fixtures so far this season, with the Italian giants having drawn 1-1 against Barcelona in the first leg of their last 16 tie.
