Unless you say otherwise, Morgan Stanley will deduct it for you, and IIRC, the don't take your exemptions into account - just 30% off the top. You get to decide

Unless you say otherwise, Morgan Stanley will deduct it for you, and IIRC, the don't take your exemptions into account - just 30% off the top. You get to decide if you want to take the tax liability or get the refund (assuming you're effective tax rate is not actually 30%).