A customer phoned to ask how much is left on their gift card. Where do I look?

Open Marketing → Gift cards and click the code in the All cards list. The card opens with what is left on it, its expiry and its status, and a movements table showing every step: issued, topped up, redeemed, refunded or cancelled, each with the amount, the order number and a note. Read the balance to them. The same view exists for store credit under Marketing → Store credit, found by their phone number, and for every house account under Settings → House accounts.