The taxmen bought a USB stick from a former tax advisor outside Germany containing huge amounts of information on tax deals across Europe, Spiegel reported.
The stick, with details of tax avoidance and illegal deals covering up to €70 billion of trade, reportedly cost the authorities €5 million.
Using the data, investigators will be able to follow up on suspicious transactions that were used to illegally escape tax and collect what's due.
The Süddeutsche Zeitung reported that investigators have bought a second cache of data covering 55,000 customers at a single bank believed to have hid money from the authorities outside Germany illegally.
Around 120,000 people have come forward and admitted to tax evasion to spare themselves potential jail time, Spiegel reported.
Authorities across Germany have collected between €4-€5 billion after buying nine such databases since 2010.
Some of the biggest scams included so-called "Cum-Ex deals", where banks and financial services companies would have the tax authorities reimburse them several times for a capital gains tax they had paid only once.
Both German and foreign banks and their customers are suspected of involvement in the fraud, and some have already come forward.
The first police raids against some of the culprits are expected to come within weeks.