Thanks for your reply. However, I'm thinking more of features. The only features I can think of is 'baby faces', no wrinkles, behaviour like buying only alcohol rather than a week's shop, being in a group, wearing fashionable clothing that is trendy amongst teenagers - is this enough? Tbh I get a little bit frustrated with the 'if in doubt' rhetoric as what it means is I end up IDing someone in their 30s who I think looks young enough to be 24 and when they explain they don't have ID because they are 30, I tell them to wait a minute while I get my colleague. Then my colleague (who has worked there far longer than I have) says 'no they are fine', and moves on, but then the customer is annoyed at us both for taking so long. I just wish there was more protocol and guidance for new workers like me, as I don't want to be wasting anybody's time, which is how the customers make me feel, but I also don't want this hanging over my head.