According to China Railway Corporation, the E-tickets have been piloted for several high speed railways since August 2019. It means passengers to travel on high speed trains running along these high speed railways do not need to print paper tickets anymore. They can use only the ID certificate used to book the ticket, most commonly passport, to enter the railway station and take the train.  
  Hong Kong, Macau and Taiwan citizens can swipe their Mainland Travel Permit to get in the railway station. For foreign passengers, it is required to go through the manual channels and board the train.
  21 stations including Shanghai Station, Shanghai West, Nanxiang North, Anting North, Huaqiao, Kunshan South, Yangchenghu, Suzhou, Wuxi, Huishan, Changzhou, Zhenjiang, Xianlin and Nanjing Station.
  Total 11 stations like Lijiang, Heqing, Dali, Yunnanyi, Nanhua, Chuxiong, Guangtong North, Lufeng South, Kunming and Kunming South.
  13 stations along the way includes Chengdu East, Jianyang South, Ziyang North, Longchang North, Dazu South, Yongchuan East, Bishan, Chongqing and Chongqing West.
  There are totally 32 stations and some are as follow:
Guangzhou South, Bijiang, Shunde, Xiaolan, Zhongshan, Zhuhai, Kaiping South, Maoming, Zhanjiang West.
  27 stations include Haikou East, Meilan, Wenchang, Qionghai, Boao, Yalongwan, Sanya, Haikou, Yintan, Yazhou, Fenghuang Airport, and Xiuying.
  If passengers need a receipt, they can get it at any ticket window of railway stations with their ID certificate used to reserve the ticket within 30 days from the date of traveling.
  The most convenient way is to handle it on the official website of China Railway Corporation. If you buy the e-ticket from an agency, ask that agency to handle it for you, because the refundment will go back to the original payment account.  

But for someone who has got the expense reimbursement receipt, they have to change or cancel tickets at the designated ticket counters in train stations.