A number of popular Japan Racing Association jockeys, including Norihiro Yokoyama, 28, have revised their income tax returns and paid a total of 220 million yen in back taxes for the three years up to 1995, tax authority sources said Jan. 23.The back taxes are a result of taxation authorities' new policy of demanding a more detailed appropriation of costs. The previous policy allowed jockeys to write off some 34 percent of their income as costs, the sources said. The jockeys were audited by the Kanto-Shinetsu Regional Tax Bureau, the sources said.The jockeys were ordered to pay back taxes on the unreported part of their incomes -- the difference between estimated expenses and actual expenses, the sources said. Last week, tax authorities reported that Yukio Okabe, 48, one of the most successful jockeys in the country, had paid 55 million yen in back taxes on some 100 million yen in unreported income for the same reason.In addition to Yokoyama, Yoshiomi Shibata, 30, Hitoshi Matoba, 39, and Matsuharu Tanaka, 25, were asked to revise their tax returns, they said. Yokoyama reportedly failed to report about 69 million yen, Shibata 58 million yen, and Matoba and Tanaka 50 million yen each for the three-year period, they said.