Around 120 former and current employees of JPMorgan Securities Japan Co. failed to declare a combined ¥700 million of income obtained mainly through stock options, sources said Saturday.

Most of them have already amended their tax returns following inspections by the Tokyo Regional Taxation Bureau, according to the sources.

It is believed that during several years through 2008, the employees executed stock options to buy shares of parent company JPMorgan Chase & Co. at a discount compared with market prices, and profited by selling them on the market. However, they failed to declare the difference as employment income, the sources said.

Many of the workers are believed to have managed and traded the shares in foreign accounts, which Japan's taxation authorities have difficulty checking.