In American societies, tips have become a form of black tax. Many feel it should go as high as 20% of the total bill and even make tips compulsory, just so that waiters can afford a living wage.
My opinion: If you feel obliged, a 5% to 10% of the total bill is decent! If your tip exceeds your VAT, then that is fairly obscene.
According to the Oxford Dictionary, a tip is “a sum of money given to someone as a reward for a service”. The point is that the service has to be proportional to the tip. It’s important to consider the overall experience, such as the waiter’s attentiveness, friendliness, and accuracy of the service when deciding on the tip amount. If you can go as high as 20%, bless your kind heart!