(Reuters) - American International Group Inc AIG.N posted a $6.7 billion fourth-quarter loss on Thursday as the U.S. insurer booked a big charge related to U.S. tax reform and losses from global catastrophes.

FILE PHOTO: A banner for American International Group Inc (AIG) hangs on the facade of the New York Stock Exchange, in New York, U.S., on October 16, 2012. REUTERS/Brendan McDermid/File Photo

Excluding one-time items, adjusted fourth-quarter earnings were $526 million, or 57 cents per share, compared with an adjusted loss of $2.8 billion, or $2.72 per share, in the same period a year earlier.

Analysts were expecting earnings of 75 cents per share, on average, according to Thomson Reuters I/B/E/S.

AIG booked $762 million of catastrophe losses during the quarter, largely from wildfires that raged through California and caused significant damage to homes and businesses.

The quarter also reflected a “modest” reserve boost to cover future claims, driven by losses in its international commercial businesses.

AIG’s general insurance business posted just $13 million in adjusted pretax income, compared with a $4.9 billion loss in the year-ago quarter, which was affected by a review that caused AIG to significantly boost reserves.

The insurer’s life and retirement business was also affected by a re-evaluation of its underlying method of predicting losses. The business booked a $90 million charge, primarily due to what AIG called a “modernization” of actuarial systems and models.

That business’ adjusted pretax income fell 10 percent to $782 million from $866 million in the year-ago quarter. Overall, AIG’s bottom line was mostly hurt by the Tax Cuts and Jobs Act, posting $6.7 billion worth of charges related to the new tax law.

U.S. tax reform has caused many financial services companies to book big one-time losses for earnings held overseas and also for an accounting oddity related to losses booked during the 2007-2009 financial crisis, even though lower corporate tax rates will help them in the long run.

Under Chief Executive Officer Brian Duperreault, who has been in the role for less than a year, AIG has been looking to acquire businesses and restructure itself to boost results, with a particular focus on technology.

The insurer now has three units, including a general insurance business, a life and retirement unit and a standalone technology unit.

In its announcement on Thursday, AIG said it had recently formed a Bermuda-based legal entity named DSA Reinsurance Company. The entity’s main purpose is to reinsure old policies the company has on its books, many of which have been contributing to losses.

Last month, AIG also agreed to purchase reinsurer Validus Holdings Ltd VR.N for $5.6 billion in a bid to expand its offerings and improve underwriting tools.