Oct 24 (Reuters) - Real estate information provider CoStar Group trimmed its annual revenue forecast on Tuesday as high interest rates forced consumers to rethink property purchases in an uncertain economy, sending its shares down 8% in extended trading.

The Washington, D.C.-based company expects annual revenue between $2.445 billion and $2.450 billion, compared with its prior estimate of $2.45 billion to $2.46 billion.

Analysts on an average expect annual revenue of $2.46 billion, according to LSEG data.

Surging mortgage rates and a tight supply of homes for sale have reduced affordability for many first-time buyers.

Brokerage William Blair said last week its survey indicated low perception among real-estate agents on the value of paying for leads through home search portals because of factors including expensiveness and low lead quality.

CoStar also forecast current-quarter revenue between $630 million and $635 million, the mid-point of which was below market estimates of $644.3 million.

The company, which competes with home-listing service providers Zillow Group and Redfin, posted revenue of $624.7 million for the quarter ended Sept. 30, missing estimates of $625.9 million.

Profit per share came in at 30 cents, unchanged from a year earlier.

Last week, CoStar said it had proposed to buy OnTheMarket, the UK's third-largest residential real estate platform, for 1.10 pound per share in cash, or about 100 million pounds ($121.63 million). ($1 = 0.8222 pounds) (Reporting by Jaspreet Singh in Bengaluru; Editing by Devika Syamnath)