This excerpt taken from the NDAQ 8-K filed Feb 20, 2008.
If an entity reporting under IFRS has a contract that is onerous, the present obligation under the contract is recognized and measured as a provision. Under U.S. GAAP, costs to terminate a contract before the end of its term is recognized as a liability and measured at fair value when the entity terminates the contract in accordance with the contract terms. A liability for costs that will continue to be incurred under a contract for its remaining term without economic benefit to the entity should be recognized and measured at its fair value when the entity ceases to use the right conveyed by the contract. OMX has identified a difference between U.S. GAAP and IFRS related to a leasehold property that has not yet been vacated and thus is not qualified as a provision in accordance with U.S. GAAP.