If you have the ability to trade on margin, will this improve your credit history/score? If you refuse to pay the margin and lack the funds to pay for the money borrowed, I understand that it can negatively affect your credit history (thusly, your score). However will that count as having a credit account open?
This discussion indicates that the accounts are not reported to credit agencies, but the post is also over a year old, and who knows how reliable the information is (it's fairly well-traveled, though). It's based on one person calling up Trans Union and E-Trade and asking people directly.
Regardless of what the credit reporting agencies or brokerages say, the fact is that brokerage margin is not reported to the credit reporting agencies. I have "borrowed" hundreds of thousands of dollars on margin from dozens of brokerages over the years and have never seen a dime of it reported nor have I ever heard of it ever being reported for someone else.
...and it's easy to see why this would be so because "borrowing" on margin isn't really borrowing at all because you always must have positive equity in the account at all times. So you aren't borrowing anything, you just have an investment contract that determines your gains/losses as if you had borrowed (in other words, it's simulated).