Bills marked with the message "Service not included" or "Tip not included" are handed out routinely to customers who did not order in German at some establishments.
The addition in English or French, usually added with a stamp or printed, does not appear on bills in German. Laws governing the hospitality and catering sector stipulate that all prices include both tax and service.
Although waiters and waitresses earn a salary and are not reliant on tips for their base income, customers are invited to round the sum up, a practice that often leads Germans to add up to 10 percent as a gratuity.
"But that gesture is completely optional," said the spokeswoman for the German hotel and gastronomy industry association Dehoga, Stefanie Heckel. "You cannot demand a tip on the bill - it is not allowed," she added, noting that she had never heard of such practices.
But AFP spoke to around 20 foreign tourists who had had similar experiences during a stay in the German capital, which this year marks 20 years since the fall of the Berlin Wall.
Over the course of three days, Daniel Dumond of France encountered such bills five times in five different eateries, to the extent that he thought Germany had changed its laws and that he was expected - like in the United States - to add at least 15 percent of the bill's sum for service.
A waitress at Friedas Schwester, a restaurant in the trendy Mitte district, said the establishment had started writing "Service not included" on its bills in response to a steep decline in tips by foreign visitors.
"It always used to be around 10 percent," said the waitress, who asked not be named. "You get a salary but that does not include tips - many customers don't know that."
Manager Uwe Reddig of another cafe in the area, Hackescher Hof, said his staff had asked him to print "Tip not included" on bills because they often felt short-changed by foreign guests.
Christian Tänzler of the Berlin tourism office has not registered a single complaint but acknowledged that such a mention could be misleading.
"It's very tricky - restaurant owners are playing around with the English word 'tip' which can be understood in a few different ways" - as the service charge or simply a tip for the server, said Taenzler, adding that such practices could "undermine Berlin's positive image."
But "there is no ambiguity to the word 'service'," Christoph Roemer of the German consumers' federation said. "If that is what they're doing, it's daylight robbery."
Berlin, with around 10,000 restaurants and more than 640 hotels, welcomed 8.5 million tourists in 2008.
No one knows how common the practice is or the total amount of "extra" tips given by tourists misled by the bills. But its prevalence is beginning to raise eyebrows.
One Saturday night this month in a popular restaurant in the bustling Hackescher Markt area of the capital, a group of tourists complained to their waiter about the "Service not included" mention on their bill of more than €150 ($210) and quickly received a new bill without the phrase.
"Sorry - the computer prints that automatically," the server said sheepishly.
But Jochen Fischer, co-founder of the group Vectron which is the German market leader in cash registers, dismisses this excuse.
"Everything on a cash register receipt must be programmed beforehand," he said. "Claiming the contrary is nonsense."