Japan and Korea: nothing. Coins left on a Tokyo table cause confusion, and a Seoul taxi driver will hand the change back. Korean hotels and some upmarket restaurants add a 10 percent service charge, so there is nothing to add. The exception is a private guide or a ryokan, and that tip goes in an envelope, handed over with both hands.
Thailand and Singapore: small or none. In Bangkok, leave the coins from the change at a street stall and ฿20 to ฿50 at a sit-down restaurant; hotels and smarter places add 10 percent and you add nothing. Singapore prints ++ on menus: 10 percent service and 9 percent GST go on top, and tipping is not part of the culture.
Southern Europe: round up. Portugal, Spain and Italy expect a few coins or 5 percent, 10 for something special, in cash. Italian bills often carry a coperto (a cover charge of a euro or three a head) or say servizio incluso, and either means the staff are paid; leave nothing on top of a servizio line. In France the menu price includes service by law, so service compris is the default; a euro or two a head on the table is kind, not owed.
Northern and Central Europe: say the total. In Germany, the Netherlands and the Czech Republic, 5 to 10 percent is normal and you do it by naming the figure when you pay: a €27 bill becomes “30, please”. Card terminals often have no tip screen, so carry coins.
The UK. London restaurants add a 12.5 percent service charge, increasingly 15 at the smarter ones. It is labeled discretionary, you may ask for it to be taken off, and since October 1, 2024 every penny must go to staff. An “admin fee” line in place of a service charge is not a tip; leave cash for the server instead.
Mexico and the US: this is pay. Mexican servers depend on the propina: 10 to 15 percent at a restaurant, 20 or 30 pesos for the person who bags your groceries or guards the car, always in pesos. In the US the card screen offers 18, 20 and 25 percent; 18 to 20 before tax is the standard at a sit-down meal, a dollar or two a drink, 15 to 20 percent in a taxi.
On the day. Read the bill before you add anything, because a service line means the tipping is done. Carry coins for the card readers with no tip option, and when in doubt in Japan or Korea, do nothing: a thank you is the tip.