Based in Budapest as a special attaché in 1944, Wallenberg set up shop in the city's Jewish Quarter providing papers to an estimated 20,000 Hungarian Jews, allowing them safe passage to Sweden.
However, the Holocaust hero's fate has been mired in mystery for decades. When Budapest fell to Soviet forces in January 1945, Wallenberg was taken into custody and never seen again.
Last year, Wallenberg's relatives called on Swedish authorities
to declare him dead and provide some semblance of closure for the family. Swedish law dictates that a person must have been missing for at least five years before the tax agency can declare the person deceased.
"Since we believe Raoul Wallenberg went missing end of July 1947, the date of death has been set five years later, which is 31 July 1952," Pia Gustafsson, a legal expert at the Swedish Tax Agency, told CNN in an emailed statement.
"Please note that this does not imply that the Tax Agency has made any judgment as to whether this is the actual date of death."
Wallenberg's family did not immediately respond to a CNN request for comment.
Wallenberg's actions towards the end of the Second World War also saw him provide protection for more than 12,000 persecuted people by sheltering them in buildings adorned with Swedish colors, which made them de facto annexes of Swedish delegation.
Desperate to do whatever he could, Wallenberg even rescued Jews from Nazi trains destined for Auschwitz.
Following his disappearance, the Swedish government asked its Soviet counterparts for information regarding Wallenberg. In 1957 deputy foreign minister Andrei Gromyko told the Swedish ambassador that the war hero had died of heart failure in Lubyanka prison -- the KGB's headquarters -- in 1947 and was cremated.
But Wallenberg's family refused to believe the Soviet account of his death and have railed for years for further investigation. The case was re-examined in 1991 when Sweden began working with Russia
. In 2000, Jan Lundvik, Sweden's former ambassador to Hungary, told Reuters that Russia no longer maintained Wallenberg died of natural causes while in captivity.
Susanne Berger is a German historian
who acted as a consultant to the Swedish-Russian working group that investigated the Wallenberg case between 1991-2001. Even after the official investigation ceased, she worked with a colleague, Vadim Birstein, asking Russia to release pertinent documentation about the case. In 2015 she founded the Raoul Wallenberg Research Initiative
, which brings together 80 researchers and organizations to pool expertise while working to obtain access to Russian archives and documentation which has, so far, remained undisclosed to the public.
"There are really serious questions and gaps in the official record in all three major phases of the Wallenberg case," she told CNN. "Obviously the most crucial is our purposes for establishing what happened to Raoul Wallenberg is to find out what happened to him when his trail breaks off in Lubyanka prison in July 1947.
"We are confident these kind of questions can be answered if we obtain access to documentation we need to see. Similarly we have not had access to documentation that is relevant and that could be helpful in determining why Raoul Wallenberg was arrested, what motivated Stalin to keep him imprisoned."