Earlier this year, amid then-Republican presidential candidate Donald Trump’s campaign promise to end taxes on tips in the U.S., the U.K. government introduced a new law to ensure that all tips are paid in full to staff, regardless of whether they were given in cash or by credit card.  

Ruth Prickett graduated from Cambridge University with a BA hons in History and has specialized in business and finance journalism for the past 20 years. She was editor of Financial Management, the magazine...