USA Account for free trading bonus on sign up

[dreilly215]

Background:

• Binary options trading company
• End users sign up and deposit funds
• End users purchase options
  • Options expire worthless
  • Options expire for profit
  • Options are traded for profit
  • Options are traded for loss

Scenario:

• Customer signs up and receives $10 in free trading money (sing up bonus)

Question:

• How do I account for for the initial "cash giveaway" free trading bonus?
  • Is this a contra revenue account?
  • Is this a deferred liability?
  • Is this a marketing expense?

Notes:

• I can see this being a contra revenue account if the end user profits but what if they don't?