Statutory & Regulatory Citations
This guide is grounded directly in the following federal and state tax statutes, Treasury regulations, and revenue rulings:
- California FTB Publication 1004 — Equity-Based Compensation Guidelines
- New York 20 NYCRR § 132.24 & TSB-M-07(7)I — Nonresident Allocation of Stock Options and RSUs
- Massachusetts 830 CMR 62.5A.1 — Non-Resident Income Tax Sourcing of Equity Awards
1. The "Earned Over the Vesting Period" Sourcing Doctrine
A pervasive myth in the technology industry is that if you receive a $600,000 four-year RSU grant while working in San Francisco or New York City, and you relocate to Seattle (WA), Austin (TX), or Miami (FL) one month before your Year 2 or Year 3 cliff vests, you will owe 0% state income tax on that vest.
In reality, high-tax states (led by California, New York, and Massachusetts) enforce strict statutory "trailing sourcing" rules on equity compensation. Because an RSU grant is awarded as compensation for services performed over the entire vesting period—from the Grant Date through the Vest Date—any state where you physically worked during that window claims the legal right to tax its proportional fraction of the vest, even if you are a bona fide nonresident on the day the shares vest.
2. Worked Calculation: Moving from California to Washington Halfway Through a 4-Year Grant
Suppose an engineer receives an RSU grant in Mountain View, California on January 1, 2024. After working in California for exactly 2.0 years (500 workdays), the engineer permanently transfers to the company’s Bellevue, Washington office on January 1, 2026.
Look at how California taxes each subsequent vest tranche after the engineer is already living and working full-time in Washington State:
Notice two critical conclusions from the table below: (1) Even two full years after leaving California (in January 2028), 50% of the Year 4 tranche of the original California grant is still taxable on a California Nonresident return (Form 540NR). (2) However, any NEW refresher grant awarded after establishing domicile and working exclusively in Washington has 0 California workdays in its grant-to-vest numerator, rendering it 100% exempt from California tax.
| Vest Event Date | Total Grant-to-Vest Workdays | CA Workdays | WA Workdays | CA Taxable % of Vest | Subject to CA Tax |
|---|---|---|---|---|---|
| Jan 1, 2026 (End of Year 2) | 500 Days | 500 Days | 0 Days | 100.0% (500 / 500) | 100% of Vest |
| Jan 1, 2027 (End of Year 3) | 750 Days | 500 Days | 250 Days | 66.67% (500 / 750) | 66.67% of Vest |
| Jan 1, 2028 (End of Year 4) | 1,000 Days | 500 Days | 500 Days | 50.00% (500 / 1,000) | 50.00% of Vest |
| New Refresher Granted After Move | 250+ Days | 0 Days | 100% WA | 0.00% | $0 (100% WA Exempt) |
3. Moving Between Two Taxing States & Preventing Double State Tax (Other State Tax Credits)
What happens if you relocate between two states that BOTH levy an income tax—for example, moving from California to New York, or from New York to Colorado?
On the date your RSUs vest, your new state of residence taxes 100% of your worldwide income as a resident, while your former state taxes the nonresident workday-allocated fraction earned prior to your move. To prevent unconstitutional double state taxation, you must file a Nonresident Return in your former state (reporting only the workday-allocated RSU fraction) and claim an "Other State Tax Credit" (such as California Schedule S or New York Form IT-112-R) on your resident return.
Calculate Your Specific RSU Tax Gap
Want to run these numbers on your own grant? Use our RSU tax calculator to estimate your 2026 federal and state withholding gap, the $184,500 Social Security cap offset, and how many extra shares to sell at vest: