The account's own form controls
Unlike real estate, where O.R.C. Section 5302.17 spells out the statutory language for survivorship, Ohio doesn't have one clean statute settling joint bank account survivorship. Instead, it's developed through case law: Ohio courts look at the form chosen when the account was opened — the signature card and account agreement on file with the bank — and treat that choice as the controlling evidence of what the depositor intended.
Hard to challenge once it's set
Once an account is shown to have been opened in survivorship form, that's treated as close to conclusive. Ohio courts will look past it only where there's evidence the depositor didn't freely and knowingly choose that form — fraud, duress, undue influence, or a lack of mental capacity at the time the account was opened. Simply disagreeing with the outcome, or a family member's later objection, isn't enough on its own.
P.O.D. accounts work the same way, without a co-owner
A payable-on-death (P.O.D.) account passes directly to the named beneficiary at the owner's death, outside probate, as long as the beneficiary outlives the owner. It's functionally the same idea as a survivorship account, but the beneficiary has no rights to the funds, and no co-ownership, until the owner actually dies — useful for an owner who wants to name a recipient without giving anyone access during life.
Life insurance and retirement accounts
Life insurance and retirement accounts like a 401(k) or IRA follow the ordinary rule: the named beneficiary receives the asset directly, outside probate, as long as they're alive when the owner dies. Either one only becomes part of the probate estate if no beneficiary was ever named, every named beneficiary predeceased the owner with no contingent beneficiary in place, or the policy or plan names the owner's own estate.
A will doesn't reach any of these
A survivorship account, a P.O.D. designation, a life insurance beneficiary, and a retirement account beneficiary all pass by the terms of the account or policy itself — not under the will. Naming someone different in a later will has no effect on any of them. The only way to change who receives the asset is to change the paperwork directly with the bank, insurer, or plan administrator, while the owner is still alive and able to sign.