You can use your old badge to enter the Canton Fair. If you have a buyer entry badge from the 104th session of the Canton Fair, it is still valid. If you forget your badge or lose it, you will have to pay 200RMB for a new one. Also you can verification you badge online first that may save your registation time at the entrace at https://www.cantonfair.org.cn/en-US/register/index
