want a deposit? When I checked out and gave credit card info and even received an email receipt, it didn't have any deposit listed.

If they want a deposit will they add it to my 1st months bill, or let me know later? When exactly does T-Mobile let you know if you need to pay a deposit if purchasing service online?

From my experience if they need a deposit they will have you pay it before they send you the phone or start your service. They don't want to get screwed out of money so they would make you pay the deposit when you checked out. Even when purchasing online they can do very quick and simple credit checks that give them enough information for them to make the decision on deposit or no deposit. Hope that makes sense!