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RSU Tax Planning

Sell-to-cover, withholding gaps, and a practical playbook for quarterly or monthly vesting.

Last updated: January 2026

RSU taxation fundamentals

RSUs are taxed as ordinary income when they vest and settle. Unlike options, there is no exercise decision — taxation is automatic at vesting.

Event	Tax treatment
Grant	No tax event
Vesting/Settlement	Full FMV taxed as ordinary income
Sale	Capital gain/loss from vesting price

The withholding gap problem

This is the most common equity comp tax surprise: employers often withhold at supplemental wage rates that are below a high earner’s true marginal rate.

Tax component	Typical withholding	Actual rate (high earner)
Federal income tax	22% supplemental rate	32–37%
Social Security	6.2% (up to wage base)	6.2%
Medicare	1.45%	2.35% (incl. surtax)
State income tax (example)	Varies	Varies

Why it hurts

On large RSU income, even a 10–15% federal gap can mean tens of thousands of dollars due at filing — and potential underpayment penalties if not managed during the year.

Strategies to address withholding gaps

Increase sell-to-cover

Where the plan administrator allows it, set federal withholding closer to the client’s actual marginal bracket (often 32%/35%/37%).

Adjust W-4 withholding

Add extra withholding on regular wages (W-4 Step 4(c)) to offset expected RSU under-withholding.

Quarterly estimated payments

Use 1040-ES and safe harbor rules (often 110% of prior year tax for high earners) to avoid penalties.

Sell additional shares

Immediately sell extra shares at vest (beyond sell-to-cover) and set cash aside for the tax gap.

Quarterly/monthly vesting cadence

Many tech companies vest RSUs monthly or quarterly. This creates multiple taxable events per year — which is both a challenge (more tracking) and an opportunity (more chances to correct course).

Advisor tip

Create a vesting calendar and schedule a proactive Q4 check-in. Review year-to-date vesting and decide whether to adjust withholding or make estimated payments before year-end.

Cost basis reporting issues

Brokers may report RSU cost basis incorrectly on Form 1099-B (often showing $0). Clients should use FMV at vest as basis and report any necessary adjustments on Form 8949 to avoid double taxation.

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