Clinical software maker athenaHealth Inc. said Thursday it will delay its fourth-quarter report so it can complete its year-end audit and review the way it records implementation fees.

AthenaHealth was scheduled to report its fourth-quarter results Friday morning. It did not say when it expects to complete the review or release its report. However, the company plans to file a notice of late filing with the Securities and Exchange Commission by Tuesday.

Thomson Reuters says analysts are expecting the company to report a profit of 18 cents per share and revenue of $55 million in the fourth quarter.

AthenaHealth said it is reviewing its accounting policy for the amortization period on the revenue it gets from implementing its services for new customers. That revenue is counted as deferred until the implementation is complete. At that time the fees are recognized at a regular rate over the expected length of the contract between the company and athenaHealth — usually one year, according to athenaHealth.

The company said it is considering whether the amortization period should be extended. If athenaHealth makes a change, it will restate financial results from previous years.

AthenaHealth reported $7.6 million in implementation and other revenue in the first nine months of 2009. That was about 5.5 percent of its total revenue.

In aftermarket trading, athenaHealth shares dropped $5.56, or 13 percent, to $37.96. The stock closed at $43.52.