Tax authorities have filed a criminal complaint against a Tokyo firm that provides betting tips on horse races, alleging it evaded some 300 million yen in corporate taxes on 1 billion yen in income during the 18-month period to March 2002, sources said Wednesday.

Tax officials suspect that Big Win, based in Shibuya Ward, and its de facto owner, Noriyuki Masuyama, 42, hid the 1 billion yen after placing ads in tabloids and magazines using more than 100 bogus company names to attract customers, who were provided odds and other betting information via telephone.

User fees were remitted to bank accounts set up under the different firm names, and Big Win excluded the sales figures from some of those accounts when it declared its income, the sources said.

Tax officials believe the company names used in the ads served only a perfunctory purpose, and that all of the hidden income is Big Win's, the sources said, noting the criminal complaint was lodged with prosecutors.

It is believed that Big Win used such a huge number of aliases to attract more customers and to avoid receiving complaints for tips that did not pan out.

The money that was hidden was kept at Masuyama's home or spent on personal expenses, the sources said.

According to credit rating firms, Big Win, established in 1999, declared income of some 350 million yen in the year to March 2002 and roughly 1.27 billion yen the following year.

Big Win acknowledged in a statement Wednesday it had been inspected by tax authorities but declined further comment.