Starting on July 15, 2019, in compliance with relevant laws in the United States, Perfect World Entertainment, Inc. will collect applicable sales tax on behalf of our users in certain states on the purchases made through Arc (www.arcgames.com).
The applicable rate of sales tax varies by location and is determined based on legal nexus. Your billing address will now be required at check out to determine your sales tax rate. The amount of sales tax charged will be added as a separate line item to your purchase and to your invoice.
The official announcement is posted here.