At IB I believe you can 'short' stocks in an IRA account but you must use your own IRA $; you cannot use/borrow/margin IB's $ in order to short stocks.
"...IRA accounts can have cash or margin trading permissions, but margin accounts are never allowed to borrow cash (have a debit balance) as per US IRS regulation...."
http://individuals.interactivebrokers.com/en/trading/tradingConfiguration.php?p=t&ib_entity=llc
http://individuals.interactivebrokers.com/en/accounts/iraClasses.php?ib_entity=llc
I hope this helps.
Tom
"...IRA accounts can have cash or margin trading permissions, but margin accounts are never allowed to borrow cash (have a debit balance) as per US IRS regulation...."
http://individuals.interactivebrokers.com/en/trading/tradingConfiguration.php?p=t&ib_entity=llc
http://individuals.interactivebrokers.com/en/accounts/iraClasses.php?ib_entity=llc
I hope this helps.
Tom
in lieu of $$