Why do you need a voided check to set up a bank link?

Custodians (like Schwab or Fidelity) need a voided check in order to confirm that your bank account’s number and registration match what we put on their bank linking form. If you don’t have checks, custodians will also accept a deposit slip (or preprinted direct deposit form) from your bank or a bank account statement that shows your full account number and account registration.