Thanks to a hard drive sent anonymously to its tax department, North Rhine Westphalia has sent details of 160,000 accounts to 19 European countries, 50,000 of them to German federal authorities, 42,540 to France and 40,022 to Belgium.
"This is a message to dodgers," the state's finance minister Norbert Walter-Borjans, a member of the Social-Democratic Party, said. "More and more of their hinding places are being found out. All over the world the danger of being discovered is growing."
The list is likely to contain some large-scale tax avoidance, according to Le Monde newspaper, and is by far the biggest the French tax inspectors have ever received.
In 2008 Italian former HSBC engineer turned whistleblower Hervé Falciani handed over details of 8,993 Swiss accounts.
France has netted 5.9 billion euros from 17,775 cases since it set up a special unit for account-holders to own up in 2013 and has nearly 30,000 others pending.