Successor Beneficiary 10-Year Clock in 2026: IRC §401(a)(9)(H)(iii), the EDB-Reset Distinction, and the Naming-Cascade Playbook

When a primary beneficiary of an inherited IRA dies before the account is fully distributed, the person who steps in next is called the successor beneficiary. The rules that govern how quickly a successor must draw the account down are found in IRC §401(a)(9)(H)(iii), clarified in the July 2024 final regulations (Treasury Decision 10001), and materially different depending on whether the deceased primary beneficiary was a non-Eligible Designated Beneficiary subject to the 10-year rule or an Eligible Designated Beneficiary using the lifetime stretch.^[1]

For a non-EDB primary — which is the majority case under the post-SECURE regime, covering nearly every adult child who inherits from a parent who died after January 1, 2020 — the 10-year clock does not reset when the primary beneficiary dies. The successor steps into the primary beneficiary's remaining window and must distribute the full balance by the original December 31 of the tenth calendar year following the original account owner's death. If the primary died in year 8 of that window, the successor has two years. If the primary died in year 2, the successor has eight. This is the single most consequential asymmetry in the inheritance code that most families do not know about until it hits them.^[2]

For an EDB primary — a surviving spouse who chose the inherited-IRA route instead of the §408(d)(3)(C) rollover, a minor child of the decedent, a disabled or chronically ill individual, or a beneficiary not more than 10 years younger than the decedent — the rule is different. When that EDB dies, the successor beneficiary does get a new 10-year window, starting from the primary beneficiary's date of death. This preserves the EDB's lifetime stretch benefit for one additional generation of tax deferral, which is a materially different outcome from the non-EDB non-reset penalty.^[3]

This article is the operating manual for the successor beneficiary rules: the IRC §401(a)(9)(H)(iii) statutory framework, the non-reset default for non-EDB primaries, the EDB-successor-reset carve-out, the annual-RMD-continuation mechanic under Treas. Reg. §1.401(a)(9)-5, the distinction between successor beneficiaries and contingent beneficiaries, custodian mechanics for inheriting an inherited IRA, three worked case studies, six planning mistakes, and the naming-cascade playbook that every primary beneficiary should execute within 30 days of accepting an inheritance. Before you dial in the numbers on any specific fact pattern, the CalcLeap retirement calculator, the Traditional IRA calculator, the Roth IRA calculator, the 401(k) withdrawal calculator, and the income tax calculator handle the year-by-year math.

Who counts as a successor beneficiary

A successor beneficiary is the individual — or trust, or estate — named on the primary beneficiary's own beneficiary form for the inherited retirement account.^[4] The primary beneficiary is the person named on the original account owner's beneficiary designation form; the successor beneficiary is one step downstream. The two roles are conceptually distinct, filed on different forms, and produce different downstream tax outcomes even though the money is the same.

An easy way to keep the vocabulary straight is to think in terms of who signed which form:

• Primary beneficiary. Named by the original account owner on the account's beneficiary designation form. Inherits at the account owner's death.
• Contingent beneficiary. Also named by the original account owner. Inherits only if the primary predeceases the account owner or executes an IRC §2518 qualified disclaimer within nine months of the account owner's death.
• Successor beneficiary. Named by the primary beneficiary on the inherited-IRA custodian's separate beneficiary form for the inherited account. Inherits at the primary beneficiary's death — regardless of what the original account owner's contingent-beneficiary form says. This is critical: the original owner's contingent beneficiary does not automatically become the successor beneficiary of the primary who took the inheritance.^[5]

The consequence of that last point is that a primary beneficiary who never files a beneficiary designation on their inherited-IRA account has effectively named their own probate estate as the successor beneficiary. That triggers a cascade of avoidable problems that we walk through in the naming-cascade section below.

The IRC §401(a)(9)(H)(iii) non-reset rule

The core statutory rule is at IRC §401(a)(9)(H)(iii). For a beneficiary who is a designated beneficiary but not an eligible designated beneficiary — the classic post-SECURE non-EDB — subparagraph (H)(ii) requires the entire interest to be distributed within 10 years after the account owner's death. Subparagraph (H)(iii) then addresses what happens if that beneficiary dies before the 10-year deadline: the successor beneficiary is subject to the same December 31 of the tenth calendar year deadline that was already running.^[6]

Treasury Decision 10001, the July 19, 2024 final regulations, made this explicit. Treas. Reg. §1.401(a)(9)-5(e)(2) states that when a designated beneficiary who is not an EDB dies before receiving the entire interest, the beneficiary of that beneficiary — the successor — must continue distributions in accordance with the same 10-year rule applied to the original beneficiary. There is no fresh 10-year window. There is only what remained of the original 10-year window at the moment the primary beneficiary died.^[7]

The core rule For a non-EDB primary beneficiary, the successor beneficiary steps into the remaining term of the primary's 10-year window. If the primary died in year 8, the successor has years 8, 9, and 10. If the primary died in year 2, the successor has years 2 through 10. There is no reset.

Worked example — the non-reset penalty

Assume Robert dies at age 78 on March 15, 2026. His Traditional IRA — balance $900,000 at date of death — passes to his adult son Marcus, age 52, as a non-EDB primary beneficiary. Because Robert died on or after his Required Beginning Date, Marcus must take annual RMDs during years 1 through 9 using his own Single Life Table divisor with the reduce-by-one convention.^[8] Marcus's year-1 divisor at age 52 is 34.4; his year-2 divisor is 33.4; and so on. Marcus takes only the minimum each year and defers the rest.

Marcus dies unexpectedly in April 2032 — year 7 of his 10-year window. The remaining account balance is $580,000. Marcus's beneficiary designation form on the inherited IRA — filed with the custodian in 2026 — names his daughter Priya, age 28. Priya is now the successor beneficiary.

Under IRC §401(a)(9)(H)(iii), Priya does not get a new 10-year window from Marcus's April 2032 death. She is bound by the original December 31, 2036 deadline (the tenth calendar year following Robert's 2026 death). Priya has years 2032, 2033, 2034, 2035, and 2036 to distribute the full $580,000 balance — approximately five years, not ten. Priya must also continue Marcus's annual-RMD divisor stream: her year-7 divisor is not looked up at Priya's age 28; it is Marcus's continuing divisor of 34.4 − 6 = 28.4 for 2032, then 27.4 in 2033, 26.4 in 2034, 25.4 in 2035, and full-balance distribution by December 31, 2036.^[9]

The compressed schedule forces Priya to absorb approximately $116,000 per year in incremental ordinary income during her peak earning years — pushing her from the 22% bracket she otherwise occupies as a mid-career professional into the 24% and 32% brackets and, in one of the two heavier years, into IRMAA and NIIT territory once she turns 50. The federal-plus-state-plus-surcharge tax bill on that $580,000 could easily exceed $175,000, versus roughly $110,000 if she had a fresh 10-year window running from her own inheritance date. The non-reset rule cost approximately $65,000.

The EDB-successor-reset carve-out

The one situation where the successor beneficiary does get a new 10-year window is when the deceased primary beneficiary was an Eligible Designated Beneficiary who was using the lifetime stretch — not the 10-year rule. IRC §401(a)(9)(H)(iii) explicitly addresses this case in its second clause: when an EDB dies before the account is fully distributed, the remaining interest must be distributed within 10 years after the EDB's death.^[10] That is a fresh 10-year window, running from the EDB's date of death — not the original account owner's.

The five EDB categories under IRC §401(a)(9)(E)(ii) that trigger the reset are:

1. Surviving spouse who chose the inherited-IRA route instead of the §408(d)(3)(C) rollover. A surviving spouse who exercised the rollover election is no longer a beneficiary — they own the account outright, so the concept of successor beneficiary does not apply. But a surviving spouse who kept the account titled as an inherited IRA — often to preserve §72(t)(2)(A)(ii) penalty-free early withdrawals — is an EDB using lifetime stretch. Their successor gets a fresh 10-year window.^[11]
2. Minor child of the decedent under age 21. Once the minor child reaches age 21, they are no longer an EDB and the 10-year clock starts running with year 10 falling in the year they turn 31. If the minor child dies before reaching age 21, their successor gets a new 10-year window starting from the minor child's date of death.^[12]
3. Disabled individual under IRC §72(m)(7). A disabled individual EDB using lifetime stretch — the successor gets a fresh 10-year window from the disabled EDB's date of death. This is a common planning-oriented outcome for Special Needs Trust structures.
4. Chronically ill individual under modified IRC §7702B(c)(2). Same treatment as disabled — successor gets a fresh 10-year window.
5. Individual not more than 10 years younger than the decedent. A sibling or life partner who inherited under the age-gap rule — successor gets a fresh 10-year window from the sibling's death.

Worked example — the EDB-successor reset

Rework the earlier hypothetical: Robert dies at age 78 in 2026 with a $900,000 IRA. This time, the primary beneficiary is his surviving spouse Elena, age 74, and Elena elects the inherited-IRA route (not the §408(d)(3)(C) rollover) so she can preserve §72(t)(2)(A)(ii) if she needs pre-59½ distributions from an account not yet owned by her — which does not apply here because Elena is over 59½, but many surviving spouses under 59½ do use this election. Elena is an EDB (spouse) using lifetime stretch under §401(a)(9)(B)(iv).

Elena dies in 2033 at age 81. The remaining IRA balance is $780,000. Elena's successor beneficiary — named on her inherited-IRA custodian form in 2026 — is her son Marcus, age 59. Under IRC §401(a)(9)(H)(iii), Marcus does get a new 10-year window starting from Elena's 2033 death. His year-10 deadline is December 31, 2043 — not the December 31, 2036 deadline that would have applied to Robert's non-EDB successor.

Marcus now has 10 years to plan the distribution, which is 7 more years than the counterfactual where Elena had elected the spousal rollover and treated the account as her own. That extra time changes the smoothing math dramatically — Marcus can retire at 65 in 2039 and take the final six years of distribution in a low-bracket retirement, saving approximately $180,000 in federal-plus-state tax versus the counterfactual where he had to absorb the entire $780,000 in his peak-earning years from age 59 to 65.

Annual RMD continuation under Treas. Reg. §1.401(a)(9)-5

Treas. Reg. §1.401(a)(9)-5(d)(1)(ii) as amended by TD 10001 addresses the annual RMD mechanic when a primary beneficiary of a post-RBD-death account dies during the 10-year window. The rule is that the successor beneficiary continues the primary beneficiary's Single Life Table divisor stream — not the successor's own divisor from the Single Life Table at the successor's age.^[13]

This is a substantial trap for young successors inheriting from older primary beneficiaries. If the primary beneficiary was age 68 when they inherited, their year-1 divisor was 20.4. By year 8 the divisor was 13.4. If the primary dies and a 32-year-old successor inherits, the successor cannot look up a fresh 51.4 divisor from Table I — they must continue the primary's 13.4 divisor stream (and reduce by 1 each subsequent year). The result is a substantially higher annual RMD than a 32-year-old would otherwise face, but that is not the biggest concern — the compressed remaining-window and the non-reset are the load-bearing constraints.

Pre-SECURE grandfathering — accounts owned by decedents who died before 2020

For accounts where the original account owner died before January 1, 2020, the pre-SECURE lifetime-stretch rules still apply to the primary beneficiary. When that pre-SECURE primary beneficiary dies during their lifetime stretch, their successor beneficiary is now subject to the 10-year rule under the SECURE Act — a fresh 10-year window running from the primary beneficiary's date of death.^[14] This is a hybrid regime where the primary got lifetime stretch and the successor gets 10 years, and it will remain in effect for the next 40+ years as long as pre-SECURE stretch beneficiaries continue drawing down accounts.

The practical impact for a family with a pre-SECURE inherited IRA is that the primary beneficiary's minimum distributions during their own lifetime stretch continue at their historic Single Life divisor, but any successor beneficiary named to inherit at the primary's death gets a straightforward 10-year window from the primary's date of death, no annual RMDs during the 10-year window (because the original account owner's post-RBD status carried over only to the primary, not the successor), and the full balance out by December 31 of the tenth calendar year after the primary's death.

Disclaimer mechanics for successor beneficiaries

A successor beneficiary who does not want to accept the inherited IRA can execute an IRC §2518 qualified disclaimer, but the mechanics differ from the primary beneficiary's disclaimer window. The nine-month clock runs from the date of the primary beneficiary's death, not the original account owner's death.^[15] The disclaimer must be in writing, delivered to the custodian, made before the successor has accepted any benefits, and the disclaimed property must pass to whoever is next in line under the primary beneficiary's own beneficiary form.

A qualified disclaimer by the successor does NOT reset the 10-year clock. Whoever ends up receiving the account after the disclaimer is still bound by whichever deadline applies to the fact pattern — the original clock for a non-EDB primary chain, or a fresh 10-year window if the primary was an EDB. Disclaimers are a control-and-family-dynamics tool, not a tax-timing tool.

The naming-cascade playbook

Every primary beneficiary who accepts an inherited retirement account should execute a naming-cascade decision within 30 days of the custodian titling the inherited IRA in the beneficiary's name. The steps:

1. Confirm custodian titling. The inherited IRA should be titled as "[Primary Beneficiary Name] as beneficiary of [Deceased Account Owner Name]." A misspelled title or a title that reads "[Primary Beneficiary Name] IRA" — without the "as beneficiary of" language — is a signal that the custodian may have inadvertently rolled the account into the primary's own IRA, which is only permitted for surviving spouses under §408(d)(3)(C) and would be a taxable event for any non-spouse.
2. File a successor beneficiary designation with the custodian. Every major custodian has an "Inherited IRA Beneficiary Designation Form" separate from the standard beneficiary form. This is the form the primary uses to name their own successor. It must be filed with the custodian — a will provision naming a "residuary beneficiary of my inherited IRA" is generally not enforceable against the custodian's paper trail.
3. Name a primary successor and at least one contingent successor. The single most common mistake is naming only one successor. If that successor predeceases the primary — or executes a §2518 disclaimer — and no contingent successor is named, the account cascades to the primary beneficiary's estate, and the estate is not a designated beneficiary. Naming a contingent successor prevents the estate default.
4. Use per stirpes or per capita language as appropriate. A successor designation of "my three children in equal shares, per stirpes" ensures that if one of the three predeceases the primary, that child's share goes to their own descendants — not to the surviving two children. Per capita would send the share to the surviving two children. Neither is universally correct — the choice depends on family structure.
5. Consider trust-as-successor for creditor-exposed or minor successors. If the primary's chosen successor is a minor, is creditor-exposed, or is on means-tested public benefits, the successor designation should name a see-through trust — either a conduit trust or an accumulation trust — following the same Treas. Reg. §1.401(a)(9)-4(f) drafting rules that apply to primary trust beneficiaries. See our see-through trust drafting guide.
6. Review and update the designation every 3-5 years and after every life event. Marriage, divorce, birth of a child, death of a named beneficiary, or a change in state of residence should all trigger a review. Beneficiary designations override wills — so a stale designation is a live risk.
7. Confirm the custodian has the up-to-date designation on file. Custodians occasionally lose or misplace beneficiary designations, particularly after mergers and acquisitions. An annual confirmation call — plus a filed physical copy in the primary's own estate documents — closes the loop.

Three worked case studies

Case 1: Priya inherits from her father Ravi (non-EDB primary, non-reset clock)

Ravi dies at age 76 on May 15, 2024 with a $1.2M Traditional IRA. His primary beneficiary is his 51-year-old daughter Nadia, a non-EDB subject to the 10-year rule. Nadia is required to take annual RMDs during years 1-9 (post-RBD death) starting at her age-51 Single Life divisor of 35.3 in 2025. Nadia takes only the minimum each year — approximately $34,000 annually — and defers the rest.

Nadia dies suddenly in July 2031, year 7 of the window. Remaining account balance: $940,000. Nadia's successor beneficiary — filed with the custodian in 2024 — is her 28-year-old daughter Priya, a college professor earning $95,000 in Massachusetts.

Under IRC §401(a)(9)(H)(iii), Priya has years 2031, 2032, 2033, and 2034 to distribute the full $940,000. She must continue Nadia's divisor stream: year-7 divisor of 35.3 − 6 = 29.3 for 2031, then 28.3, 27.3, and the full-balance flush in 2034. That produces annual RMDs of approximately $32,000, $33,000, $34,500, and then $840,500 in year 10.

Priya's total 4-year federal-plus-state tax bill on the $940,000: approximately $325,000 (35% blended after Massachusetts 5% + federal 22-32% brackets + NIIT + IRMAA at ages 30 onward). If Priya had a fresh 10-year window from Nadia's 2031 death instead of the compressed 4-year window, she could smooth $94,000/year at a 22% federal + 5% Massachusetts blended marginal, producing a total tax bill of approximately $215,000. The non-reset penalty cost her approximately $110,000.

Case 2: Marcus inherits from his mother Elena (spousal EDB primary, fresh 10-year window)

Elena dies at age 81 on January 20, 2033 with a $780,000 inherited IRA that she had received when her husband Robert died at age 78 in 2026. Elena elected the inherited-IRA route in 2026 (not the §408(d)(3)(C) rollover) because she was 74 and wanted to preserve access to a portion of the account without disturbing her own accounts, and as a surviving-spouse EDB she was using lifetime stretch under §401(a)(9)(B)(iv). Her successor beneficiary — named on the inherited-IRA custodian form in 2026 — is her son Marcus, age 59, a Texas resident earning $180,000 as a corporate finance director.

Under IRC §401(a)(9)(H)(iii), Marcus gets a fresh 10-year window starting from Elena's January 20, 2033 death. His deadline is December 31, 2043 — 10 full years. Because Elena died before her Required Beginning Date-equivalent for spousal EDBs (the year Robert would have turned 73, already past), the successor treatment applies with the same post-RBD annual-RMD rules — but Marcus can also elect the 10-year alternative treating the account as if Elena died before RBD, giving him full flexibility.

Marcus plans to retire at 65 in 2039. His strategy: take $50,000/year during his peak-earning years 2033 through 2038 (at a 24% federal + 0% Texas blended rate), then $130,000/year during his low-bracket retirement years 2039 through 2043 (at a 22% blended rate). Total 10-year federal tax: approximately $175,000. Counterfactual if he had to distribute the full $780,000 in 2033-2038: total tax approximately $260,000. The EDB-successor-reset preserved approximately $85,000.

Case 3: Diana disclaims and the cascade activates

Diana's father Marcus (from Case 2) dies unexpectedly in 2038 at age 64 during his peak-earning years, with a remaining inherited-IRA balance of $560,000. Diana is age 34, a physician earning $340,000 in California, married to a corporate lawyer earning $280,000. The $560,000 inherited-IRA balance would land in the 35%-37% federal bracket, plus 12.3% California state, plus IRMAA, plus NIIT — a combined marginal rate approaching 55%.

Diana's mother is 60 and earns $70,000 as a school administrator, sits solidly in the 22% federal bracket, and lives in Nevada. She was named as the contingent successor beneficiary on Marcus's naming cascade when he set it up in 2033. Diana executes an IRC §2518 qualified disclaimer within 9 months of Marcus's 2038 death — before accepting any distributions or exercising any investment discretion. The account cascades to Marcus's contingent successor, Diana's mother.

Diana's mother is bound by the same 10-year deadline Marcus was working under: December 31, 2043 (10 years from Elena's original 2033 death). She has 2038 through 2043 — 6 years — to distribute $560,000. At approximately $95,000/year, that lands at a 22% federal + 0% Nevada blended rate for a total tax of approximately $124,000. Counterfactual if Diana had accepted: approximately $290,000. The disclaimer preserved approximately $165,000 for the family.

This case is the reason the naming-cascade playbook matters. The disclaimer only worked because Marcus named a contingent successor. Without one, the account would have gone to Marcus's estate, forced probate, and probably ended up subject to the 5-year rule under §401(a)(9)(B)(ii) — closing off both the disclaimer path and the 10-year path.

Six most-common planning mistakes

1. Never filing a successor beneficiary designation on the inherited IRA. Cascade defaults to the primary beneficiary's estate. Estate is not a designated beneficiary — the account may be forced into the 5-year rule and probate.
2. Assuming the original owner's contingent beneficiary automatically becomes the successor. The contingent-beneficiary form is signed by the original account owner and applies only if the primary predeceases the owner or disclaims within 9 months of the owner's death. It is irrelevant to what happens after the primary has already accepted the inheritance.
3. Assuming the 10-year clock resets when the primary dies. For a non-EDB primary — which is the majority of post-SECURE inheritances — the clock does not reset. The successor is bound by the original deadline.
4. Failing to name a contingent successor. If the named successor predeceases the primary or disclaims, the account cascades to the primary's estate — the same trap as never naming a successor at all.
5. Missing the disclaimer window. The 9-month clock for a successor's §2518 disclaimer runs from the primary beneficiary's death, not from the original owner's death. Missing it locks the successor into ordinary-income tax exposure on the full remaining balance.
6. Assuming the successor can restart the primary's Single Life divisor at the successor's own age. Treas. Reg. §1.401(a)(9)-5(d)(1)(ii) requires the successor to continue the primary's divisor stream with the reduce-by-one convention. Any calculator or advisor that pulls a fresh divisor from Table I at the successor's age is wrong for this fact pattern.

State-tax overlay for the successor

Successor beneficiaries face the same four-tier state-tax framework as primary beneficiaries, but with one extra planning constraint: the successor typically has less time to plan around a state-of-residence change than a primary would. In Case 1 above, Priya had four years to consider whether to relocate from Massachusetts (5% flat rate on retirement income) to Florida or Texas (no state income tax) to save on the $940,000 distribution stream — but a bona fide domicile change under Cal. Rev. & Tax. §17014 or its analogs typically requires at least 12 months, and the compressed window may not permit it.

The tier structure is unchanged from the primary-beneficiary case:

• Tier 1 (no state income tax). AK, FL, NV, NH, SD, TN, TX, WA, WY. Zero state tax on distributions.
• Tier 2 (full retirement income exclusion). IL, IA, MS, PA, MI (2026 onward for eligible birth years). Zero state tax on retirement-plan distributions including inherited-IRA distributions in most cases.
• Tier 3 (partial exclusion, age-tiered or income-tiered). GA, SC, KY, NC, CO, and others. Partial state tax with credits and exclusions.
• Tier 4 (full inclusion). CA, NJ, NY, VT, MN, and others. Full state tax on retirement-plan distributions including inherited-IRA distributions, at rates up to 13.3% California marginal.

See the state-specific field guides for California, Illinois, New Jersey, and Pennsylvania on the CalcLeap blog for the detailed state-by-state mechanics: California §401(k) and IRA basis, Illinois §401(k) and retirement taxation, New Jersey §401(k) and §457 basis, and Pennsylvania §401(k) after-tax basis.

8-item action checklist

For a primary beneficiary who just accepted an inherited retirement account:

1. Confirm custodian titling within 30 days. The account should read "[Your Name] as beneficiary of [Deceased]" — not "[Your Name] IRA."
2. File a successor beneficiary designation with the custodian within 30 days. Use the custodian's specific inherited-IRA beneficiary form.
3. Name a primary successor and at least one contingent successor. Never file with only one named person.
4. Use per stirpes or per capita language deliberately. Model both outcomes with your estate attorney against realistic mortality assumptions.
5. Consider a see-through trust for creditor-exposed or minor successors. Follow Treas. Reg. §1.401(a)(9)-4(f) drafting rules — same as primary trust beneficiaries.
6. Retain a copy of every filed designation in your own estate file. Custodians occasionally lose paperwork; keep independent proof.
7. Review every 3-5 years and after every life event. Marriage, divorce, birth, death of a named successor, state move — all trigger reviews.
8. Communicate the plan to your named successors. The naming cascade only works if your successors know they are named — they need to know to file their own disclaimer within 9 months if they don't want the account.

Frequently asked questions