Executive summary

When a married couple faced a $420,000 RSU vesting event in 2025, a coordinated plan of staged sales, targeted tax‑loss harvesting, front‑loaded retirement deferrals and donor‑advised fund (DAF) bunching materially reduced incremental tax and smoothed cash flow. Updated through September 2026, this case study shows how those same levers remain effective in 2026 tax practice — with additional attention now paid to NIIT, state withholding, safe‑harbor estimated payments and donating shares directly to charity.

Background

The clients: a married couple in their early 40s, two children, filing jointly. Primary earner W‑2 salary in 2025: $280,000. Employer granted RSUs that vested during 2025 with a taxable value at vesting of $420,000. The clients also held a taxable brokerage account showing $72,000 of unrealized long‑term losses and reported about $24,000 of other itemizable deductions after SALT limits.

Key constraints: employer withholding on supplemental wages (RSU income) was limited; the couple wanted to avoid unnecessary short‑term capital gains, reduce federal tax bite in the spike year, and prevent underpayment penalties.

Challenge

The RSU vesting produced two distinct tax consequences:

  • Ordinary income at vesting equal to the fair market value of the vested shares, which could push the couple into higher marginal tax brackets and trigger surtaxes (NIIT) or Medicare IRMAA effects.
  • Subsequent sale of those shares creates capital gains or losses measured from the FMV at vesting; timing of sales determines whether gains qualify as long‑term (>1 year) or short‑term.

By mid‑2025 the couple faced a potential combined ordinary and capital gains tax bill large enough to create cash‑flow stress and a risk of underpayment penalty if withholding and estimated payments weren’t corrected.

Solution

The adviser proposed a coordinated, multi‑part plan executed across Q3–Q4 2025 and into early 2026. Core elements remain recommended in 2026 practice with a few refinements based on recent trends and tax‑administration focus areas:

  1. Staged sales of RSU shares. Sell only what’s needed at vesting to cover taxes and living expenses; schedule additional sales later to spread capital‑gain recognition and increase the likelihood of long‑term treatment for shares held past one year.
  2. Tax‑loss harvesting in the taxable account. Realize $72,000 of long‑term losses to offset capital gains from RSU sales while respecting wash‑sale rules and documenting lot sales for tax reporting.
  3. Maximize pre‑tax retirement deferrals. Increase 401(k) deferrals to the plan maximum available for the year to lower AGI and blunt the margin‑bracket effect of the RSU income.
  4. Charitable bunching via DAF and direct gifts of shares. Bunch three years’ worth of charitable giving into a DAF to boost itemized deductions in 2025, and where appropriate donate appreciated shares directly to DAFs or public charities to avoid realizing capital gains on donated stock.
  5. Align withholding and estimated taxes using safe‑harbor rules. Use employer withholding adjustments plus quarterly estimated payments calibrated to safe‑harbor thresholds to avoid underpayment penalties (either 90% of current‑year liability or 100%/110% of prior‑year tax as applicable).
  6. State withholding and NIIT planning. Model state income tax impact of the RSU event; evaluate whether additional state withholding or estimated payments are required. Also model exposure to the 3.8% Net Investment Income Tax (NIIT) and Medicare surtaxes.

Implementation — timeline and concrete moves

Execution unfolded across five months in 2025 with follow‑through in early 2026; the same sequencing is recommended for similar 2026 events.

  • At vesting (June 2025): The couple sold approximately 40% of the vested shares to fund withholding and cash needs. Employer withheld at the supplemental rate; adviser recommended immediate supplemental estimated payments to reach an overall effective withholding closer to the couple’s marginal tax rate.
  • July–September 2025: Realized $72,000 of long‑term losses by selling loss lots in the taxable account. To preserve losses, the adviser did not repurchase substantially identical securities within 30 days and reallocated proceeds into diversified ETFs after the wash‑sale window where needed.
  • August–September 2025: Increased 401(k) elective deferrals to the plan maximum for the remainder of 2025, reducing AGI by roughly $19,500 (approximate; subject to plan limits and catch‑up rules where applicable).
  • October 2025: Contributed $45,000 to a donor‑advised fund to bunch anticipated charitable giving into 2025. The adviser also recommended donating a portion of appreciated non‑RSU shares directly to charity where applicable to avoid capital gains.
  • Quarterly payments and withholding: Adjusted estimated‑tax payments in Q3 and Q4 and increased W‑4 withholding for the high earner in Q4 to reduce underpayment risk. The adviser documented safe‑harbor calculations to justify payment strategy in case of audit.

Results — numbers and tax impact

All figures below are illustrative and rounded to reflect the couple’s facts and the adviser’s model.

  • Baseline without planning: Salary $280,000 + RSU ordinary income $420,000 = $700,000 of ordinary income, which would have pushed substantial income into higher marginal brackets and increased exposure to NIIT and Medicare surtaxes.
  • AGI and deduction changes: Front‑loading retirement deferrals reduced AGI by ~ $19,500. Bunching charitable contributions into a DAF added $45,000 of itemized deductions for 2025, producing an approximate $64,500 immediate tax‑base reduction versus the unplanned scenario.
  • Capital offset: $72,000 of harvested long‑term losses offset long‑term gains from RSU sales dollar‑for‑dollar in 2025 and created carryforwards for 2026 if unused.
  • Estimated tax alignment: Supplemental estimated payments and increased withholding eliminated projected underpayment penalties and reduced the need for a large cash reserve at filing.
  • Net effect: The coordinated moves produced an estimated mid five‑figure reduction in incremental federal tax versus a “sell everything now” baseline and smoothed cash flow, while preserving long‑term holding options. The capital‑gain exposure on shares sold after vesting was largely neutralized by harvested losses; ordinary‑income tax at vesting remained the dominant tax cost.

Why the approach still works in 2026 — and what’s new

  • Staged sales remain a simple way to manage timing and the long‑term/short‑term distinction. In 2026, volatility in some sectors makes waiting for the one‑year holding mark more attractive when downside risk is manageable.
  • Tax‑loss harvesting continues to be highly effective for offsetting capital gains and creating carryforwards. In 2026 advisers are documenting wash‑sale avoidance more rigorously given increasingly automated IRS matching of lot sales.
  • DAF bunching retains its value for taxpayers who itemize in high‑income years. Additionally, donating appreciated shares directly to charities or DAFs is now more frequently recommended to avoid realizing capital gains before donating.
  • Safe‑harbor estimated payment strategies (90% current year or 100%/110% of prior year) are essential in 2026 planning to avoid underpayment penalties — particularly when employer supplemental withholding understates marginal exposure.
  • State tax and NIIT modeling is more central to planning: with larger RSU events, the 3.8% NIIT and state‑level surtaxes can meaningfully change optimal timing for sales and charitable strategies.

Lessons learned

  1. Model the full tax stack: ordinary income, capital gains, NIIT, Medicare surtaxes and state taxes before deciding sales timing.
  2. Document loss‑harvest lots and wash‑sale avoidance carefully; automated IRS matching has raised the stakes for precise lot accounting.
  3. Consider donating appreciated stock directly to charity or to a DAF when charitable intent exists to avoid a capital‑gains realization event.
  4. Use safe‑harbor rules for estimated payments and track withholding across employers and state jurisdictions to avoid penalties.
  5. Run year‑over‑year scenarios (current year and next) — staging sales across calendar years can materially affect effective tax rates and NIIT exposure.

Takeaways

  • Staged RSU sales plus targeted loss harvesting remain a high‑impact, tested strategy for managing concentrated equity events.
  • Front‑loading retirement deferrals and bunching charitable deductions into a DAF can reduce taxable income in a spike year — combine these levers for amplified effect.
  • Model NIIT and state taxes; they are often the marginal drivers of additional tax on large RSU events in 2026.
  • Document decisions, lot sales and payment calculations; precision matters when IRS automated systems and state notices increase scrutiny.
  • Plan estimated payments early; safe‑harbor thresholds are the practical guardrail against underpayment penalties.

FAQ — Common questions for similar RSU events

Should I sell RSUs immediately at vesting or hold for long‑term gains?

It depends on cash needs, concentration risk, and tax consequences. Immediate sale reduces market risk and provides cash for taxes; staged sales allow you to time recognition, potentially qualify for long‑term capital gains if you hold past one year, and smooth tax‑year impacts. Model both paths, including NIIT and state tax effects.

Can I offset RSU capital gains with losses in my taxable account?

Yes. Long‑term losses offset long‑term gains dollar‑for‑dollar. In this case, $72,000 of long‑term losses neutralized comparable long‑term gains from RSU sales. Be careful with wash‑sale rules and ensure you document lot sales and repurchases to preserve losses.

Is bunching to a DAF still worthwhile in 2026?

Yes, when you expect a high‑income year and you itemize after bunching. DAFs provide immediate deduction timing and grant flexibility. Also consider donating appreciated shares directly to avoid realizing capital gains prior to donation.

How do I avoid underpayment penalties after a big RSU vest?

Recalculate projected tax liability as soon as the vesting is known. Use increased W‑4 withholding, make quarterly estimated payments and rely on safe‑harbor rules (90% of current year or 100%/110% of prior year) to avoid penalties. Keep records of the calculations used.

What extra items should be modeled now (2026)?

In 2026, include NIIT exposure, Medicare surtax effects, state‑by‑state withholding needs, and potential changes in employer withholding practices. Also factor in the utility of donating appreciated shares directly and the availability of tax‑loss carryforwards into future years.