Three specific requirements
Under Estates Code § 113.151, sums remaining on deposit at a party's death belong to the surviving party or parties only if the deceased party's interest was made to survive by a written agreement, signed by that party. Subsection (c) is explicit that this agreement "may not be inferred from the mere fact that the account is a joint account or that the account is designated as JT TEN, Joint Tenancy, or joint, or with other similar language." The label on the account means nothing without the signed agreement behind it.
The exclusive method, confirmed by the Supreme Court
The Texas Supreme Court addressed this directly in Stauffer v. Henderson (1990), holding that the statute provides the exclusive means for creating a right of survivorship in a joint account, and that a written agreement signed by the decedent is necessary to do it. There's no informal or implied workaround — without that signed writing, a joint account simply doesn't carry survivorship rights under Texas law, no matter how the parties may have understood their arrangement.
A clear agreement can't be second-guessed later
When the written agreement is unambiguous and complete, Texas courts won't look past it. Outside testimony — parol evidence — about what the parties actually intended is inadmissible to vary the terms of an unambiguous, complete survivorship agreement. That cuts both ways: it protects an agreement that clearly grants survivorship from being challenged after the fact, and it means a family member can't argue their way around a clear agreement that doesn't favor them, just as much as they can't invent survivorship where none was written.
A statutory form makes this easy to get right
Since 1993, Texas has provided standard statutory language financial institutions can use, allowing a depositor to select survivorship by initialing next to a statement such as: "MULTIPLE-PARTY ACCOUNT WITH RIGHT OF SURVIVORSHIP." Using this kind of form, adapted into the current Estates Code, is a straightforward way to satisfy the statute's requirements without drafting a custom agreement from scratch.
The bank is protected once it follows the agreement
A financial institution that pays a surviving party in accordance with a valid written survivorship agreement isn't liable to an heir, devisee, or beneficiary of the deceased party's estate for having done so. This protection is exactly why banks rely so heavily on getting the signed agreement in place at account opening — it's their shield against a later dispute over where the money should have gone.
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 becomes part of the probate estate only 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.