Hospitals would have to disclose the discounted prices they negotiate with insurance companies under a Trump administration rule that could upend the $1 trillion hospital industry by revealing rates long guarded as trade secrets.

Hospitals that fail to share the discounted prices in an online form could be fined up to $300 a day, according to the proposal. The price-disclosure requirements would cover all the more than 6,000 hospitals that accept Medicare, as well as some others, and is likely to face fierce industry opposition.

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