For remote workers pricing up a desk in Da Nang, Hanoi or Ho Chi Minh City who need to know both the number on the price list and which payment method the front desk will actually accept.

For anyone buying lanterns, T-shirts or a bottle of rose myrtle wine after dark and wondering which stalls will take a scan and which still want notes.

A practical guide to group dinners in Vietnam — what the till can and cannot do, who should hold the bill, and how everyone gets paid back.

For anyone landing at Noi Bai, Tan Son Nhat or Da Nang who wants to know exactly what the ride into town costs and which payment method will actually work at the kerb.

For anyone buying water, beer and instant noodles across Vietnam who wants one payment method that works at a city chain store and at a village shop with no card machine.

For travellers whose Visa or Mastercard keeps failing on VietJet or Vietnam Airlines, with separate verdicts depending on whether you are in Hanoi or three hours from the nearest ticket office.

For coffee drinkers who start in the Hanoi Old Quarter and end up somewhere with one ATM and no card machine — which payment method to rely on, and where each one breaks.

For visitors who want to tip properly in Vietnam, keep the right notes on them, and recover cleanly when the money goes to the wrong place or the wrong person.

For anyone renting a scooter in Hanoi, Hoi An or Da Nang who wants their deposit back, their passport in their own pocket, and no argument on the last morning.