It's necessary to tax self-employed online sellers, a former official with the State Administration of Taxation said at the China Tax Law Forum in Beijing on Friday.

"If we don't tax online sellers, who nowadays not only sell petty commodities but even houses and vehicles, we will not have so much to tax in the future," said Li Linjun, vice-chairman and secretary-general of the China Certified Tax Agents Association and a former department chief of the State Administration of Taxation.

In 2012, online sales in China were more than 1.3 trillion yuan. The more than 7 million self-employed online sellers, whose sales volume reached 800 billion yuan, on Taobao, a popular online marketplace, didn't pay taxes, Li said at the forum.

Li said there are many challenges for the taxation on online sellers. Tens of thousands of people are making a living from online sales and it will cause fear and unrest and the market will be disrupted if they were to pay taxes immediately, Li said.