When siblings inherit a 401(k) together, the split is governed by the beneficiary designation form the account holder filed with the plan, not by the will or any family understanding. Each sibling’s share is calculated from that form, transferred into a separately titled Inherited IRA (or paid out as a lump sum), and then drawn down on that sibling’s own schedule under the 10-year distribution rule. The pieces move independently after the split, so one sibling’s choices do not bind the others.
The Beneficiary Form Controls the Split
Call the plan administrator first and ask for two documents: a copy of the beneficiary designation on file and a copy of the plan document itself. Together they answer who gets what and what each person is allowed to do with it. A will that says something different does not override the form.
If the form names the siblings equally, the administrator divides the account into equal shares. Named percentages control when they are specified. Two terms in the designation change how a deceased sibling’s share moves: per stirpes sends that share down to the deceased sibling’s children, while per capita redistributes it among the surviving siblings.
Each sibling has to be certified by the plan administrator as a designated beneficiary before any money moves. No transfer, rollover, or distribution happens until that certification is complete for the person requesting it.
When No Beneficiary Was Named
If the account holder never filed a beneficiary form, the plan document’s default provisions decide who inherits. There is no universal federal hierarchy. Plans commonly default to the surviving spouse first, then children, then the estate. When the estate becomes the beneficiary, the 401(k) is pulled into probate, which adds cost and delay and generally means worse tax treatment because an estate is not an individual beneficiary and faces a compressed distribution timeline. Ask the administrator for the plan’s default beneficiary language in writing.
Each Sibling’s Two Paths
Once shares are certified, every sibling makes an independent choice: take the money as a lump sum, or move it into an Inherited IRA. The right answer usually depends on that sibling’s tax bracket and cash needs, but sometimes the plan itself removes the choice.
Lump Sum
Taking the full share in cash puts the entire pre-tax balance on that year’s tax return as ordinary income. The plan administrator withholds 20% for federal taxes off the top, and the actual bill can be higher or lower depending on total income for the year.1Internal Revenue Service. Topic No. 412, Lump-Sum Distributions A Roth 401(k) held by the original owner for at least five years is generally tax-free on distribution.2Internal Revenue Service. Retirement Topics – Beneficiary Once cashed out, the money loses its tax-advantaged status for good.
Direct Rollover to an Inherited IRA
The more common choice is a direct trustee-to-trustee transfer of the sibling’s share into an Inherited IRA (sometimes called a Beneficiary IRA). Because the funds move institution to institution without passing through the sibling’s hands, the 20% mandatory withholding does not apply.1Internal Revenue Service. Topic No. 412, Lump-Sum Distributions
The Inherited IRA must be titled to identify it as an inherited account, typically along the lines of “[Deceased Owner’s Name] IRA, FBO [Beneficiary’s Name].” Formats vary by custodian, but the account has to link the original owner to the beneficiary on its face.3Fidelity. Inheriting an IRA From Your Spouse Improper titling can be treated as if the full balance were distributed and taxed. A non-spouse beneficiary cannot roll the inherited money into a personal IRA or an employer plan; it stays in a separate Inherited IRA and is never mixed with the sibling’s own retirement savings.4Ascensus. What You Need to Know When Accepting Inherited Retirement Assets
The Plan May Limit These Options
Some 401(k) plans require non-spouse beneficiaries to take a lump sum and do not permit an Inherited IRA rollover at all. Others impose a shorter distribution window than the IRS 10-year maximum. Before building any multi-year tax plan, call the administrator and ask specifically what distribution methods the plan document allows for non-spouse beneficiaries.5Fidelity. Inherited 401(k): What to Know if You’re a 401(k) Beneficiary If the plan forces a full payout, the Inherited IRA strategy is not available.
The 10-Year Rule
The SECURE Act of 2019 ended the old life-expectancy “stretch” for most non-spouse beneficiaries. When the original owner died after 2019, each sibling generally has to empty their share by December 31 of the tenth year after the year of death.2Internal Revenue Service. Retirement Topics – Beneficiary Each sibling’s 10-year clock runs on their own share, independently of what other siblings do.
Missing the deadline triggers a 25% excise tax on the remaining balance. That penalty drops to 10% if corrected within two years.6Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs
Whether Annual RMDs Are Required Inside the 10 Years
The most common mistake here comes from missing a split within the rule. If the original owner died before reaching their required beginning date for RMDs (currently age 73), the sibling can withdraw in any amounts, in any years, as long as the account is empty by year ten.6Internal Revenue Service. Retirement Plan and IRA Required Minimum Distributions FAQs If the owner died on or after their required beginning date, the sibling must take annual minimum distributions in years one through nine based on their own life expectancy, and still empty the account by the end of year ten.
The IRS provided penalty relief for missed annual RMDs during 2021 through 2024 while these rules were being finalized.7Internal Revenue Service. Notice 2024-35, Certain Required Minimum Distributions for 2024 That relief has ended. Starting in 2025, missing an annual distribution can trigger the 25% excise tax. So every sibling needs to know one thing early: how old was the account owner at death, and had they started RMDs?
Roth 401(k) Balances Still Have the 10-Year Deadline
An inherited Roth 401(k) also has to be emptied within 10 years. Qualified distributions come out income-tax free if the original owner held the account for at least five years, so the tax pressure on timing is lower, but the account still has to be drained by that final December 31.2Internal Revenue Service. Retirement Topics – Beneficiary
Siblings Who Are Not Bound by the 10-Year Rule
A short list of “eligible designated beneficiaries” can still stretch distributions over life expectancy:
- The surviving spouse of the account owner
- Minor children of the account owner (not grandchildren), until they reach the age of majority, when the 10-year clock then starts
- Disabled or chronically ill individuals as defined by the IRS
- Beneficiaries no more than 10 years younger than the deceased account owner
That last category catches more siblings than people expect. A sibling within 10 years of the deceased’s age qualifies for the stretch, which over decades can be worth a great deal in tax deferral. A sibling who is disabled or chronically ill under the IRS definition can also qualify on their own share, even if the other siblings cannot.8Vanguard. RMD Rules for Inherited IRAs
Timing Withdrawals to Control the Tax Hit
For a traditional pre-tax inherited 401(k), every dollar withdrawn is ordinary income in the year taken. Where annual RMDs are not mandatory, the sibling controls the timing across the 10 years, and the goal is usually to avoid bunching income.
Spreading roughly evenly across ten years is the default that keeps a sibling out of higher brackets. Even is not always optimal, though. A year of lower income, whether from a job change, parental leave, or early retirement, is the year to pull more. A year with a home sale or large stock option exercise is a year to pull less, if annual RMDs are not required for that share.
The instinct to wait until year ten and let the account grow untouched usually backfires. A $500,000 balance withdrawn in a single year can push a sibling from the 24% bracket into the 35% bracket. Taking roughly $50,000 a year for ten years keeps far more of the money in lower brackets, even accounting for the lost growth on money withdrawn earlier.
Siblings inherit the same account, but they do not inherit the same tax situation. One sibling in a high-earning year and another between jobs will have opposite optimal schedules. Each person plans their own share.
The Transfer Sequence
Doing the mechanical steps out of order creates delays and, in a few cases, accidental taxable events.
Notify the plan administrator. Send a certified copy of the death certificate and request the non-spouse beneficiary claim forms. Each sibling submits their own paperwork. If a trust is a beneficiary, the administrator will also need the trust document and a trustee certification.
Open the Inherited IRA before requesting the distribution. The receiving account has to exist and be properly titled as an inherited account before the 401(k) sends any funds. Setting it up first prevents the situation where money arrives at an account that does not exist or is registered incorrectly.
Handle the year-of-death RMD. If the original owner was required to take an RMD for the year they died and had not yet taken it, that amount has to come out of the 401(k) before the remaining balance moves. The year-of-death RMD cannot be rolled into the Inherited IRA. The siblings split it according to their ownership percentages.9Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs)
Request a direct trustee-to-trustee transfer. Each sibling instructs the 401(k) administrator to send their share directly to their Inherited IRA custodian, with the receiving account number on the distribution form. Direct movement avoids the 20% withholding and keeps the money tax-deferred.1Internal Revenue Service. Topic No. 412, Lump-Sum Distributions
Expect four to eight weeks for the transfer, sometimes longer. Start early if an annual RMD is due for the year.
Disclaiming a Share
A sibling who does not want their share can formally disclaim it. A qualified disclaimer causes the disclaimed portion to pass as if the disclaiming sibling had died before the account owner, which usually sends the money to contingent beneficiaries or to the remaining siblings depending on how the form reads.
Federal law is strict about what counts. The disclaimer must be in writing, delivered to the plan administrator within nine months of the original owner’s death, and the disclaiming sibling must not have accepted any benefit from the account, including any distribution.10Office of the Law Revision Counsel. 26 USC 2518 – Disclaimers Once even a partial distribution is taken, the rest cannot be disclaimed. The nine-month clock runs from the date of death, not from when probate closes or the plan finishes processing claims.
Disclaiming can make sense when a sibling is in a much higher bracket than the contingent beneficiaries, or when the sibling wants the inheritance to go to their own children without gift tax consequences.
When the Split Goes Sideways
Most 401(k) splits close cleanly when the beneficiary form is current and unambiguous. Trouble tends to come from an outdated form (an ex-spouse still listed, for example), siblings who dispute the form’s validity, or an administrator who delays.
If the administrator denies a claim or drags out processing, the first step is the plan’s internal appeal. For retirement benefit claims, the appeal deadline can be as short as 60 days from the denial letter, and the letter itself will state the deadline and the process. ERISA requires exhaustion of the internal appeal before a beneficiary can sue in federal court.
Sibling-versus-sibling disputes about what the form should have said are a different fight. Courts have consistently held that the plan’s beneficiary designation controls, even when a will says otherwise. Arguing that a form was signed under duress or was about to be changed is a heavy legal lift and usually requires federal court litigation.