We all know what to do with surly wait staff and belligerent baristas. We deny them their tip. It’s the only way they’ll learn.

But what happens when the shoe is on the other foot? When a customer’s rudeness comes to the fore? A Spanish café has come up with a solution, landing a palpable hit for put-upon service types everywhere.

It’s decided to “tax” the rude.

According to a sign in the window of the Restaurant Blau Grifeu in Llança, on the Costa Brava in Catalonia, customers will now be charged a whopping €5 (A$7.37) if they fail to say please when ordering coffee. Those who use their manners will pay €3 ($A4.42), while those who greet staff with a hearty “Buenos días!” will only have to cough up €1.30 (A$1.92).

The café’s owner, Marisel Valencia Madrid, said the sign had “made all the difference”.

“People are now super polite in all matters and it has really improved daily life,” she said in an interview with the English-language Spanish news site The Local. “Yesterday some children even told their parents to say please, so it’s working!”

Indeed, the sign has been so effective that the 41-year-old hasn’t had to tax anyone yet.

“Everyone is giving me a greeting and saying please,” she said. “Some even say thank you now too.”

“I’m surprised at the attention but it’s good to remind people to be polite to everyone, even when ordering a coffee.”

In 2014, a café on the New South Wales south coast made headlines after it offered customers discounts for using the word “please” when ordering.

Kylie Pickett, co-owner of Seven Mile Beach Kiosk in Gerroa, south of Wollongong, said at the time that “the whole idea behind [the sign] is to put a smile on people’s faces before they come in the door.”

“For all the guys who work here it’s such a nice experience. To say ‘please’ [just] takes a second and it makes all the difference.”