Josh the diver
Contributor
I would add for charter ops that some want to know when your last dive was. just to make sure it has not been a year or to since your last dive, so you don't need a refresher.If you want nitrox fills, you will have to show your nitrox card at least the first time at a shop.
Many shops want to see your cert card at least the first time you want fills.
You can buy gear without showing a cert card.
Charter ops really differ. Some want an idea of your experience, others just want to see a card.