If you enter a venue (for example, a shop, restaurant, religious centre or sports stadium) that has an official NHS COVID-19 QR code poster at the entrance, you scan it with your app. Read more about how to tell whether a QR code poster is an official NHS one.

If other people were at the same venue at the same time as you, and later test positive for coronavirus (COVID-19), you may get an alert to let you know. Read more about how it's decided whether you get an alert.