The Nowsnapp service fee (and banknote amount) is charged only when your deal is complete.
To mark a deal complete, both you and the Acting Member need to both mark the deal as complete and give each other ratings. (This will otherwise be done automatically by the system after six days.)
As a Posting Member, you may see a Pre-Authorisation Charge on your credit card statement when you’ve confirmed your Acting Member and the banknote turns Black. Don’t worry - this is simply a check to make sure you have enough to complete the deal.