Microsoft may owe Denmark more than 5.8 billion kroner (£672 million) in unpaid taxes and interest, according to a report from Denmark's national broadcasting corporation, DR.
The tax arrears are related to Microsoft's $1.3 billion (£860 million) acquisition of the Denmark-based financial software firm Navision more than a decade ago in July 2002.
Danish tax authorities are investigating allegations that Microsoft dodged the taxes in question by using sneaky workarounds.
According to DR, Microsoft sold some of Navision's divisions to its own Ireland-based subsidiary, allegedly in an effort to shift Navision's revenues overseas and into jurisdictions where tax rates are much lower than those in Denmark.
Other major tech firms, including Google and Facebook, have recently been embroiled in similar tax-dodging allegations.