The 19-year-old sensation had agreed to sign an improved deal with Santos in November, but his contract was only submitted to the Brazilian Football Confederation (CBF) on Friday.
Neymar's previous deal expired in February 2015, but the Brazil international has now agreed to commit his future to Santos only until the summer of 2014.
This means that the 2011 Fifa Puskas award winner may leave the club on a free transfer after the upcoming World Cup in Brazil.
The Santos star, who has 15 international caps to his name, is believed to be courted by Spanish duo Real Madrid and Barcelona.
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