Tax authorities believe Yuko Matsuoka, the Japanese translator of the global best-seller "Harry Potter" series, failed to declare 3.5 billion yen in income in the three years to 2004, sources said Wednesday.

Matsuoka, 62, did not declare her income in Japan, saying she lived in Switzerland, but tax authorities consider her a resident of Japan and have ordered her to pay more than 700 million yen in back taxes, the sources said.

Matsuoka has filed an appeal and requested that the Japanese and Swiss governments hold consultations to reach an accord to prevent double taxation, according to the sources.

Matsuoka took over the post of president of Tokyo's Say-zan-sha Publications Ltd. from her husband after he died in 1997, but she left the post last December. She is currently serving as a company director.

Since 1999, she has translated the "Harry Potter" series of British author J.K. Rowling and the Japanese versions have been published by the company.

The sources said Matsuoka received large amounts of translation fees from the company and did not declare the income in Japan, but rather in Switzerland, claiming she moved her residential registration in 2001.

Japan taxes residents on all income, whether it is earned in or outside Japan. Residents of other countries who gain income in Japan are required to pay Japanese tax.

In Switzerland, the tax rate on the equivalent of the income in the Matsuoka case would be less than 40 percent, compared with 50 percent in Japan, according to the sources.