The Catalan club have allowed an allocation of 40,000 to attend Camp Nou due to coronavirus restrictions, but at present only 31,213 tickets have been requested by their supporters.
According to the Daily Mail, Barca are surprised that almost 8,000 tickets remain unclaimed, despite their season tickets including entrance to Champions League games.
Tickets for the match against the Bundesliga champions are now on general sale, with prices ranging from £93 (€109) to £170 (€199).
Tuesday's match is not only Barcelona's first European fixture without club legend Lionel Messi, who joined Paris Saint-Germain this summer, but is also their first against Bayern since the Germans thrashed them 8-2 in the Champions League quarter-finals in August 2020.
This is not the first time since the coronavirus pandemic that Barca have not sold out their ticket allocation at home, as there were around 1,000 unsold tickets for last month's league clash with Getafe, even though 20,000 fans were allowed to attend. body check tags ::