The German Deutsche Bank has refused to give up Trump's records in the past when they were requested by congressional Democrats, but the bank has now complied with a subpoena from special counsel Robert Mueller.
From The Guardian:
Deutsche Bank, the German bank that serves as Trump’s biggest lender, was forced to submit documents about its client relationship with the president and some of his family members, who are also Deutsche clients, after Mueller issued the bank with a subpoena for information, according to multiple media reports. The news was first reported by Handelsblatt, the German newspaper.
The revelation makes it clear that Mueller and his team are investigating the president’s finances. Trump’s son-in-law and White House adviser, Jared Kushner, is also a client.
As you probably know, Trump has done business with Deutsche Bank for years because American banks refused to do business with him following several bankruptcies that screwed virtually everyone involved in them from the banks themselves to local cities and counties. Trump has been a walking financial disaster for decades.
Deutsche Bank was fined $10 billion for its involvement in a Russian money laundering scheme earlier this year and we know the Trump family receives a lot of capital from Russians thanks to Eric Trump's big mouth.
This is pure speculation on my part, but it's possible Mueller is actually more interested in Jared Kushner's finances than Trump's. We know Kushner has been at the center of numerous shady business deals and he also ran Trump's digital campaign operation.