Brokers are always concerned... if you trade youself into a debit in your account, can you pony-up to honor your obligations? Self-employed are statistically more likely unable to do so than those with a well-paying job.... So, more scrutiny. (You might be self-employed and making a bundle... then again, you might be a dog walker making $600/mo.) Financial institutions usually want "verification of income/assets". Self-employeds often weak in that area. (I know.. I've been self/un-employed my entire life.)
Ahhh the debit. The debit usually only happens in situations like limit up/down moves or huge gaps after a weekend? basically when their system can't auto-liquidate when the account falls below maintenance margin?
The customer's account goes into debit when his losses exceed his account, regardless of the "reason"... he's wiped out his account balance and owes money to the broker.... and the broker wants to be able to collect.
I can't believe that I am defending IB after suffering their shit software for years, but they have added TradingView as their charting partner, and now you get their charts on TWS. Really easy to trade futures.