A screenshot is only a picture
A transfer screenshot might be real, might be a transfer that failed, or might be edited. You can’t tell by looking.
Same at the counter: a customer holds up a "success" screen, the queue is long, and you wave them through.
Trust it when it’s in your account
Simple rule: hand over the goods when you yourself see the money in your account, through your bank’s notice or the software you use. Not the customer’s screen.
If they say they paid and you can’t see it, ask them to check their banking app, or wait a bit and look again.
How Hensa does it
With Hensa, an order only turns paid when the money has really reached your account and matched that order. You get a notice in the app and by email the moment it lands, at the counter or online. Hensa POS, in the works, will show it right on the register. No screenshots needed.