There were even guides on how to request for a digital receipt in baidu.

As a mean to protest, the players grouped up and started spamming the company with their request for receipt, essentially overwhelming the company. One day, someone posted in Baidu (a forum similar to Reddit) that players have the right to ask for invoice/digital receipt for whatever they purchased virtually. Basically the company was doing something that pissed all the players off, but the management was playing deaf (just like what mihoyo's doing right now). The whole invoice request thing originated from the chinese FGO community/ DFO community.

For all of you who are as confused as I was, I can provide you with some contexts.