Quote from jackpearson:
How about both the trading account & an IRA account, $250k cash in each, with the same retail broker? Will both be SIPC insured?
I'm not claiming to be an expert on this, but I have called SIPC in the past. At one broker, each "person" is allowed one claim. If you have multiple accounts, it would be included in one claim. Your max protection under SIPC is the SIPC limits on your combined accounts. SIPC only covers the loss, you can't assume the loss is total, so you might be fine anyway. But, you won't get paid for both over the SIPC limits if the loss needs to be replaced.
Again, if you use an entity for your personal trading, it would be considered another "person", as long as you use the EIN#.