CMS provided an update explaining why some EP's who attested have not recieved their incentive check with the 6 - 8 week timeframe.
The maximum incentive check is $18,000 or 75% of the Medicare Allowed amount, whichever is less. When an EP hits $24,000 in Medicare allowable they have reached the maximum incentive amount. If an EP attests, and they have not yet met the $24,000 threshold the check is held until that threshold is reached. This way the EP does not have to apply for the balance and CMS does not have to write 2 or more checks.
If at the end of the year the EP still has not reached $24,000 in Medicar Allowable a check for the amount the EP is entitle to will be processed.
This means that even if you have not yet reached the $24,000 threshold but you have met 90 consecutive days of Meaningful Use you can attest now and the check will be sent when you reach the maximum incentive payment.