Concerned about illicit money flowing into luxury real estate, the Treasury Department said Wednesday that it would begin identifying and tracking secret buyers of high-end properties.

The initiative will start in two of the nation’s major destinations for global wealth: Manhattan and Miami-Dade County. It will shine a light on the darkest corner of the real estate market: all-cash purchases made by shell companies that often shield purchasers’ identities.

It is the first time the federal government has required real estate companies to disclose names behind all-cash transactions, and it is likely to send shudders through the real estate industry, which has benefited enormously in recent years from a building boom increasingly dependent on wealthy, secretive buyers.

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