Athene Holding Ltd., the insurer tied to Apollo Global Management LLC, withdrew its first-quarter financial results amid flaws tied to its accounting for reserves and taxes.

The data for the period “can no longer be relied upon and have been removed from the AAA website, effective today,” Athene Chief Financial Officer Brenda Cushing said in a letter published Thursday on the website of Apollo Alternative Assets. The company’s review will probably show an increase in net income and book value, she wrote.

Athene is working to improve financial reporting as it plans for the possibility of a public offering. The insurer said in October that it hired Tom Daula as chief risk officer and added Rich Burness as global head of tax. The lapses relate to its control over financial reporting tied to the purchase of a U.S. life and annuity business from Aviva Plc in 2013.

“We are highly focused on implementing robust public- company processes and controls before publishing revised first quarter 2014 and the remaining 2014 quarterly results,” Cushing wrote. “We have increased staffing levels and have reviewed our processes for timely preparation of support for our tax accounting positions.”

The insurer released some data Thursday about its financial condition as of Sept. 30. The company said it had consolidated statutory capital of $5.3 billion, excluding an undrawn commitment of about $1.05 billion from a fundraising effort. Athene reported assets of $59 billion using metrics that differ from U.S. generally accepted accounting principles.

Mortgage Bets

The insurer’s strategy has been to expand through acquisitions, including the Aviva transaction and a deal last month to acquire German subsidiaries of Delta Lloyd NV. The purchases give the firm more funds to invest in holdings such as mortgage-backed securities and corporate bonds.

“Based on our internal estimates, in the 15 months since closing the Aviva USA transaction we have purchased $14.1 billion of longterm investments at an average yield of 6.93 percent, which is in excess of management’s expectations at transaction close,” Cushing wrote.

AP Alternative Assets LP, which was established by Leon Black’s New York-based Apollo Global Management, is Athene’s largest shareholder, the insurer has said.