Rewrites throughout, adds shares and analyst comments

By Himanshi Akhand

Feb 13 (Reuters) - Insurance Australia Group IAG.AX posted a 54% surge in first-half cash earnings on Thursday but its top-line growth and dividend missed estimates, and it forecast lower gross written premiums (GWP) growth, sending its shares down over 9%.

The Sydney-headquartered company said it expects GWP growth for fiscal 2025 to come in at the lower end of its mid-to-high single digit forecast, as improving claims trends and lower reinsurance costs are driving a moderation in premium increases.

It reported GWP of A$8.43 billion ($5.29 billion) for the six months ended December 31, missing Visible Alpha consensus estimate of A$8.60 billion.

"Top-line growth will clearly be an issue for debate," Citi analysts said, adding that "some may be disappointed in the absence of a further buyback".

IAG's shares dropped 9.2%, as of 2347 GMT, and were among the worst performers on ASX200 benchmark index .AXJO, which was up 0.2%.

IAG said it expects annual insurance margin to come in at the top end of its prior forecast range of 13.5% to 15.5%, due to "positive momentum" in the underlying performance of its businesses.

Citi analysts believe margin forecast seems to allow for a "very conservative" catastrophic cost allowance for the second half, especially considering that natural hazard experience for January and February is already A$100 million above allowance.

The company's natural perils costs were A$215 million below its allowance for the first half.

That coupled with stronger insurance margin of 19%, sent IAG's cash earnings to A$640 million for July-December, from A$415 million last year, beating the Visible Alpha consensus of A$605.3 million.

Its net profit after tax also rose 91% to A$778 million.

The general insurer announced an interim dividend of 12 Australian cents per share, up from 10 Australian cents a year ago, but lower than consensus estimate of 13.9 Australian cents.

($1 = 1.5924 Australian dollars)

(Reporting by Himanshi Akhand and Sneha Kumar in Bengaluru; Editing by Alan Barona and Rashmi Aich)

((Himanshi.Akhand@thomsonreuters.comSneha.Kumar@thomsonreuters.com))