AT&T Inc. said it would take a $1 billion charge against earnings tied to the federal health-care overhaul, joining a number of other companies in reporting an impact from the bill signed into law this week.

The charges relate to prescription-drug benefits for retirees. Companies that provide this benefit, as AT&T does, receive a federal subsidy, plus they can deduct the value of this subsidy from their taxes. The health overhaul cancels the deductibility of the subsidy.

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