Designing a who-pays-the-fee interface

I still walk around with cash in my wallet. Not a lot of it, but enough to pay for at least a meal plus a drink. Where I live today, most people can get by their day with just their mobile phone. I’ve had friends lose their wallet and not realise until a few days later because they simply didn’t need it. If they misplaced their phone, it’d be a different matter, I’m sure. Paying for stuff and giving other people money happens mostly digitally these days. Not a major deal these days, especially within a country. India has UPI, Brazil has Pix, the Southeast-asian countries have their own digital payment systems often tied to either a national ID or mobile number. Usually, within a country, these systems don’t incur extra fees. If I send my friend SGD10, my friend receives SGD10. Straightforward. Things get more complicated when you’re dealing with cross-border payments. For myself, until 2023 when I ran into some friends I hadn’t seen in a while in Spain during WeyWeyWeb, we were still having trouble paying each other after a meal.