What is the difference between USD Debit Interest and USD Net Short Stock Interest?

Buying on margin is borrowing cash to open a new position. If the aggregate cash balance in a given account is a debit (negative balance), then funds are being borrowed and the loan is subject to interest charges. Note that even if the aggregate cash balance is a credit, a loan may still exist as a result of balance netting or timing differences…

As the assets in an IRA account are not eligible to be pledged as loan collateral, and stock ordinarily serves as the collateral securing payment of a margin loan, account holders are not permitted to buy stock on margin in either a Cash or Margin type IRA account. All stock purchases must be paid for in full with cash.  In addition, other transactions which require a margin account such as shorting stock and selling uncovered options are not allowed in either a Cash or Margin type IRA account…

Short Sales Proceeds Interest (SSPI) is the positive interest rate IBKR pays on short stock cash proceeds according to the Securities Financing page of our website.

This is a credit to the account…

You cannot simply use cash received from a short sale to meet the margin requirement for a new order in your account. A short stock sale is a margin transaction in which the account holder is borrowing stock rather than cash. While the proceeds from the short sale are credited to the cash balance of the account, these funds must be posted with the lender of the shares as collateral to secure their return. As a result, and in recognition of the fact that the loan transaction is subject to its own financing terms, the cash collateralizing the loan is excluded for the purpose of determining whether a margin loan exists…