A prosecutor for the region of Madrid confirmed via statement that new tax charges have been made against Xabi Alonso along with Angel Di Maria and Ricardo Carvalho, all former Real Madrid players.
The prosecutor's office said it acted on information from Spain's tax authorities. Alonso, the 35-year-old Bayern Munich midfielder was already under investigation by the tax agency for a 2014 case.
The current investigation in the Spanish capital also involves Di Maria, now at Paris Saint-Germain, as well as Monaco centre-back Carvalho and Real Madrid left-back Fabio Coentrao. Ex-Atletico Madrid striker Radamel Falcao has also attracted scrutiny from the Spanish tax authorities.
Alonso, who wasn't named in the recent Football Leaks, is the only one of the players who isn't a client of agent Jorge Mendes.
According to reports in the Spanish media, the authorities are seeking a back payment of around €3m from Alonso -- plus the same amount as a fine and interest for tax irregularities, while still a Real player.
Alonso has been under investigation by the Spanish authorities since 2014 for alleged tax evasion involving his image rights. The World Cup winner defended himself last year against the allegations, saying he had "fulfilled each and every one of his fiscal obligations."
Alonso, who recently turned 35, played for Real Madrid between 2009 and 2014, told Bloomberg last year he had "a diversified portfolio" in his investments.
After winning the Champions League in his final season at Real under Carlo Ancelotti, Alonso opted to join Pep Guardiola's Bayern in August 2014. His current deal with the German champions expires next summer.