IBKR currently does not support funding an RSP account via check from a RSP account at another financial institution.
Additional Information
Can I fund a RSP account at IBKR from a RSP at another financial institution via check?
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How do I transfer Securities and Cash from my current ISK Account to IBKR?
How can I resolve name mismatches or verification issues when linking external accounts?
How do I transfer funds to my TFSA account?
How do I transfer funds to my RSP account?