$100K Severance at 24%: Lump Sum vs Salary Continuation

You have a $100,000 severance package. Your YTD wages are $120,000. Adding the severance puts you at $220,000 for 2026 — well into the 24% bracket as a single filer, with about $22,700 of the severance reaching into the 32% bracket (which starts at $197,301 for single filers under IRS Rev. Proc. 2025-32). The 22% mandatory supplemental withholding under IRC §3402(o) was never designed for incomes at this level. The real federal tax on your severance is approximately $25,500. You will be underwithheld by roughly $3,500 — that's the April 15 surprise most laid-off employees don't see coming.

The quick answer: A $100K severance in the 24% bracket triggers $22K of mandatory IRC §3402(o) supplemental withholding — but actual federal tax owed is $25,816. The $3,816 gap is the April surprise. Continuation usually wins.

The federal income tax math on $100K severance

Severance is ordinary income taxed at standard rates — the only special rule is the supplemental withholding mechanic under Treas. Reg. §31.3402(g)-1. With $120K of YTD wages, here is how the $100K severance fills the brackets for a single filer in 2026:

• $0 to $11,925: 10% bracket — already filled by wages
• $11,926 to $48,475: 12% bracket — already filled
• $48,476 to $103,350: 22% bracket — already filled
• $103,351 to $197,300: 24% bracket — wages fill $103,351 to $120,000; severance fills $120,000 to $197,300 ($77,300 × 24% = $18,552)
• $197,301 to $250,525: 32% bracket — severance fills $197,301 to $220,000 ($22,700 × 32% = $7,264)
• Total federal income tax on $100K severance: $25,816

The 22% mandatory withholding produces only $22,000. You are short $3,816 at year-end. That underwithholding might also trigger an estimated-tax underpayment penalty under IRC §6654 if your total withholding falls below safe harbor (100% of last year's tax or 90% of this year's, with the 110% rule for AGI over $150K).

FICA and the Social Security wage-base cap

Under IRC §3121(a), severance is wages subject to FICA. The Supreme Court confirmed this in United States v. Quality Stores, 134 S. Ct. 1395 (2014). The 2026 Social Security wage base is $181,800 per SSA Press Release 2025-10.

With $120K of YTD wages, you have $61,800 of Social Security wage-base remaining ($181,800 − $120,000). On a $100K severance:

• Social Security tax: $61,800 × 6.2% = $3,832 (only on the first $61,800 of severance; the remaining $38,200 escapes Social Security tax)
• Medicare tax: $100,000 × 1.45% = $1,450 (no cap)
• Additional Medicare Tax under IRC §3101(b)(2): kicks in on wages over $200K for single filers. Total YTD + severance = $220K, so $20K is subject to the additional 0.9%: $180
• Total FICA: $5,462

Compared to a $50K severance recipient at the 22% bracket, the FICA effective rate here is actually lower (5.46% vs 7.65%) because of the Social Security wage-base cap. The cap effectively gives high earners a partial FICA break on the upper severance dollars.

Why salary continuation usually wins at the $100K level

Three reasons continuation typically beats lump sum at this severance amount, beyond the cash-flow smoothing argument:

1. 401(k) deferral from continuation payments

Under IRC §402(g), the 2026 401(k) employee deferral limit is $24,500 ($32,500 with age 50+ catch-up). Most 401(k) plan documents define "compensation" to include severance paid as salary continuation while you remain on payroll. Lump-sum severance paid after termination usually does NOT qualify for 401(k) deferrals (the plan typically defines "eligible compensation" as wages received while actively employed).

For a $100K severance paid as six $16,667 monthly payments, you could defer up to $16,667 per month into your 401(k) until you hit the $24,500 limit. At a 24% federal marginal rate plus state tax, deferring $24,500 saves approximately $6,000-$8,500 in current-year tax. If you're 50+ and have not yet hit the $32,500 catch-up limit, the savings increase proportionally.

Check your plan document for two specific provisions: (1) does the plan allow deferrals from severance paid as continuation, and (2) what is the termination date the plan uses for cutoff? If your last day of active work is March 31 but you remain on payroll through September 30 during salary continuation, the plan's definition of "separation from service" under IRC §409A determines whether the continuation pay is eligible for deferral.

2. Spreading withholding to match liability

The 22% mandatory withholding on a $100K lump sum leaves you $3,816 short at April. If paid as six $16,667 monthly payments, each payment triggers $3,667 of 22% withholding ($22,000 total) — same shortfall arithmetically. But spreading the payments lets you make estimated tax payments under IRC §6654 along the way to cover the gap, avoiding both the cash crunch and the underpayment penalty.

Alternatively, your employer can use the "aggregate withholding" method (Treas. Reg. §31.3402(g)-1(a)(7)) — adding the severance payment to your most recent regular paycheck and computing withholding as if the combined amount were a single regular paycheck. This usually produces higher withholding for taxpayers in the 24%+ bracket because the IRS withholding tables assume the combined amount represents annualized income. Aggregate withholding is the employer's choice, but many will accommodate the request — especially for departing employees with no continuing payroll relationship to disrupt.

3. State tax timing and relocation

If you plan to relocate to a no-tax state (TX, FL, NV, WA, SD, WY, TN, AK, NH) after the layoff, the source-of-income rules matter. Lump-sum severance paid before you establish residency in the new state is subject to your former state's income tax. Salary continuation paid after the move may also be partially subject to former-state tax — California (CCR §17951-5) and New York (NY Tax Law §631) both have aggressive rules treating severance as "deferred compensation" sourced to the state where the underlying work was performed.

For a $100K severance, the difference between paying 9.3% California state tax ($9,300) and $0 Texas tax can be material — but only if the structure and timing actually work to source the income out of the former state. Check with a state-tax-conformity-aware CPA before relying on this.

Worked example: Chicago marketing director, $100K severance

A Chicago-based marketing director, single filer, age 42, with $120,000 of YTD 2026 wages, is laid off in July 2026. She has a $620K 401(k) balance and a $130K Roth IRA. Her employer offers $100,000 either as a lump sum in August or as six $16,667 monthly payments through January 2027.

Lump sum scenario (August 2026)

• Federal supplemental withholding: $100,000 × 22% = $22,000
• Illinois supplemental withholding: $100,000 × 4.95% = $4,950
• FICA: $3,832 SS + $1,450 Medicare + $180 Additional Medicare = $5,462
• Net check: $100,000 − $22,000 − $4,950 − $5,462 = $67,588
• 2026 MAGI: $220,000 (no ACA PTC)
• Federal tax owed at filing: approximately $3,816 underwithheld + potential IRC §6654 penalty
• UI: Illinois treats lump sum as not affecting current weekly benefit; she starts collecting $578/week ($2,505/month) immediately after the layoff

Salary continuation scenario (Aug 2026 - Jan 2027, $16,667/month)

• Each monthly payment: $16,667 × (22% + 4.95% + 7.65%) = $5,772 withheld (before SS cap kicks in)
• Monthly net: $10,895 × 6 months = $65,370 total net (slightly less than lump sum due to spreading effect on FICA)
• 2026 MAGI (Aug-Dec, 5 months × $16,667): $120,000 wages + $83,335 severance = $203,335
• 2027 MAGI (Jan, 1 month × $16,667): $16,667 severance + any new wages + UI
• UI: Illinois delays UI until salary continuation ends in January 2027 — at $578/week, this costs her 22-26 weeks of UI eligibility timing (~$12,700)

Key planning lever for the Chicago director: structure the continuation so that $16,667 falls into January 2027. Her 2027 MAGI starts with that severance. If she finds a new job in March 2027 at $150K, her 2027 total income is approximately $140K — but if she remains job-searching and only has unemployment plus the January severance ($16,667 + ~$15,000 UI = $31,667), she could qualify for ACA PTC for the rest of 2027 worth $4,000-$6,000 in subsidies. The cross-year spreading is worth real money.

Same Chicago director, but with 401(k) deferral from continuation

If her 401(k) plan allows deferrals from salary continuation and she has not yet maxed out 2026 contributions (she had deferred $14,000 YTD), she can defer the remaining $10,500 ($24,500 limit − $14,000 YTD) from her August severance payment. At her 24% federal marginal rate plus 4.95% Illinois rate, that's approximately $3,041 in tax savings — converting taxable cash into pre-tax retirement balance.

Lump sum can sometimes also be 401(k)-deferrable depending on plan document, but most plans treat post-termination lump sums as non-eligible compensation. Continuation is the safer structural bet for this lever.

The state-tax overlay at $100K severance

Combined with the ~$25,816 federal income tax and $5,462 FICA, total tax burden ranges from $31,278 (in no-tax states) to $40,578 (in California) — between 31% and 41% of the gross severance.

Why the lump sum sometimes still wins

• Employer financial stress. If the company is sliding toward bankruptcy or restructuring, unpaid future severance becomes an unsecured creditor claim. The 2008-2009 wave of severance defaults wiped out salary continuations for thousands of laid-off workers. Lump sum cleared into your bank account is yours.
• You expect to be in a higher bracket next year. If you're negotiating with a competitor for a $250K role starting in Q1 2027, severance paid as continuation in 2027 sits in the 32% federal bracket (or higher with state stacking). Lump sum in 2026 locks the severance into the lower-bracket year.
• The continuation has a mitigation/offset clause. If the separation agreement reduces or terminates continuation upon new employment, and you have a strong pipeline of interviews, the offset risk is real. Lump sum is unconditional.
• Mortgage refinancing or major purchase in flight. Lenders generally won't count salary continuation as "qualifying income" for new loans (because continuation has a defined endpoint). Lump-sum cash in the bank is also not income for underwriting, but it boosts reserves — which improves DTI ratios and loan terms.

The 401(k) loan and severance-period planning

Note: If you have an outstanding 401(k) loan at the time of layoff, IRS rules require the loan to be repaid by the due date of your tax return for the year of separation (typically April 15 of the following year, plus extensions) or be treated as a taxable distribution. The Tax Cuts and Jobs Act of 2017 extended this from the previous 60-day window. For someone with a $40K 401(k) loan, missing this deadline means the $40K is treated as a distribution — taxed at the 24% bracket ($9,600 federal) plus 10% early-withdrawal penalty under IRC §72(t) if under 59½ ($4,000), plus state tax. Total potential cost: $15K-$18K on a $40K balance. Repay the loan from severance proceeds if at all possible.

The decision matrix for $100K severance in the 24%+ bracket

Estimated payments to cover the supplemental withholding gap

If you take the lump sum and don't want to fight the underpayment penalty, IRC §6654(d)(1)(B) gives you safe harbor by paying through quarterly estimated payments (Form 1040-ES) equal to:

• 100% of your prior-year total tax liability (110% if your prior-year AGI exceeded $150K), or
• 90% of your current-year total tax liability

For a Chicago director with $200K of 2025 AGI and total tax of $42K, the safe harbor for 2026 is 110% × $42K = $46,200. If her 2026 withholding from the $120K of pre-severance wages was approximately $25K, she needs an additional $21,200 in estimated payments or withholding from the severance to meet safe harbor. The $22K of supplemental withholding from the lump sum gets her over the line — but if she doesn't make any estimated payments and total withholding falls below the threshold, she faces a penalty of approximately 8% annualized on the underpayment under current IRS rates.

For salary continuation, the same calculation applies but the withholding is spread across 6 months, giving you visibility to make quarterly estimated payments through EFTPS or IRS Direct Pay as needed.

Key takeaways

• $100K severance for a single filer with $120K of YTD wages spans the 24% and 32% federal brackets; total federal income tax is approximately $25,816.
• The 22% mandatory supplemental withholding under IRC §3402(o) leaves you $3,816 underwithheld — make estimated payments under IRC §6654 to avoid the penalty.
• FICA is roughly $5,462, partly reduced by the Social Security wage-base cap ($181,800 in 2026) once your total wages cross it.
• Salary continuation usually wins for three reasons: 401(k) deferral eligibility while still on payroll, smoother withholding gap management, and cross-year MAGI spreading for ACA PTC.
• Lump sum wins when employer bankruptcy risk is real, you expect a higher tax bracket next year, the continuation has a mitigation/offset clause, or you need cash reserves for refinancing.
• State tax adds 0% to ~9.3% on top of federal; total effective tax rate ranges from 31% (no-tax state) to 41% (California top brackets).
• Repay any outstanding 401(k) loan from severance proceeds — failure to repay by the tax return due date triggers a deemed distribution taxed plus 10% penalty.