The free trial and the paper trading accounts are by default margin type accounts and this configuration can not be changed.
Can I downgrade my free trial account from a Margin type account to a Cash type account?
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How can I change my account type between margin and cash, and what are the implications?
How do I change the Base Currency for my free trial account?
Can I open a free trial account for IBKR Lite?
How does margin work in Paper Trading accounts, and can I use or simulate Portfolio Margin?