Miyajima visitor tax

I just found out that when using a JR West Rail Pass for the Miyajima Ferry, the passenger has to pay 100 yen visitor tax. I would like to ask how exactly will the tax be collected? Do I pay it at the ferry terminal on land, near Miyajimaguchi station, or do I pay it when entering the island itself? Thanks.

You can pay the tax at vending machines at the ferry teminal.