Is it possible to restrict the amount I can withdraw from my account?

While you can create a unique 2nd user name for a given individual on different accounts, IBKR does not support linking of 2nd users across different accounts, even if those accounts themselves are linked to a common primary user. This linking feature is only offered to primary account holders…

When you open a margin account you have the ability to borrow from IBKR. You can not set a limit or a set only a specific amount of margin to use in a margin account. If the account has sufficient Available Funds then a new order would be accepted. There is a calculated margin requirement for positions in a margin type account displayed as an Initial margin and Maintenance margin requirement. In addition to contracts traded in the account any borrowed cash from Forex trading or from trading outside the account’s Base Currency can have a calculated margin requirement. There are tools available so you can monitor your account’s margin requirements and cash balances in real time or as a daily snapshot…

You may withdraw up to the positive settled cash balance that you hold in the specific currency that you are withdrawing. If your balance in that currency is zero or negative, you cannot withdraw any amount in that currency, even if other currencies in your account have positive balances…

Unfortunately, this is not possible. The system will allow you to withdraw the amount of available currency you hold in the case of cash accounts. If you have a margin account, the system will allow you to withdraw funds up to the available margin amount. …