Where is it customary to pay upfront?

[moonlight]

I've heard Japan is one. Any others? I'm traveling to UK/France soon, so I'm curious about those two places in particular.

[MscleLovr]

I’ve never heard of people paying upfront in Europe…except to a scammer.

I suppose that it’s possible that a newbie might be very nervous and request this.
But as long as you stay polite, it should not be an issue.
One compromise might be to have your payment in an envelope and keep it in sight until you hand it over afterwards.

[ACluelessGent]

In Europe the usual is to pay after. 

However, I often pay upfront to get it out of the way and to make sure I don't forget it. 

Edited 58 minutes ago by ACluelessGent