RSU Cost Basis: Vesting Income, Sale Reporting & Double-Tax Risk

RSU cost basis is the tax and accounting starting point you use to measure capital gain or loss when you later sell shares received from restricted stock units (RSUs). In practice, the cost basis for RSU shares is the value that is treated as ordinary income when the shares vest (commonly the fair market value at vesting); any later gain or loss on sale is measured against that basis FINRA, Fidelity. This article defines the term, shows the calculation, walks through a transparent worked example, compares closely related equity concepts, and gives a short checklist of what to verify in your records.

What RSU Cost Basis Means

Cost basis is the tax accounting “starting value” assigned to shares you own. For RSU shares, cost basis represents the dollar amount you use to calculate capital gain or loss when you sell. RSUs are a form of equity compensation that are granted to employees without an upfront purchase requirement and generally provide limited ownership rights until vesting FINRA. Tax rules treat the value you receive when RSUs vest as ordinary income; that income amount becomes the base against which future sales are measured, i.e., your cost basis Fidelity.

Scope and what cost basis does not cover:

• Cost basis is not the same as projected future value; it’s historical—what you were treated as receiving for tax purposes on the vest date.
• When you sell, “profit” means the gain at sale over that cost basis; tax treatment of that gain (short- vs long-term) depends on how long you held the shares after vesting Fidelity.

How It Works

Mechanics overview (step-by-step):

1. Vesting event: When RSUs vest, you receive shares (or cash equivalent). The company typically recognizes the market value you received as taxable compensation for the vesting tax year. That recognized value is the monetary amount that will form your cost basis. Cite: RSUs are granted without out-of-pocket cost and are a type of stock award FINRA.
2. Cost-basis assignment: The value recognized at vesting—often the fair market value (FMV) per share multiplied by the number of shares that vested—is treated as income and becomes your tax cost basis for those shares. When you later sell, your capital gain or loss equals sale proceeds minus that basis Fidelity.
3. Holding period and tax rate: The holding period that determines short- vs long-term capital gain timing begins on the vest date; gains after more than one year post-vest may qualify for long-term rates (this is a timing rule implicit in capital-gains rules described by tax guidance; see sources on capital gain treatment) Fidelity.

Simple formula (conceptual):

• Cost basis per share = Income recognized at vesting / number of vested shares.
• Capital gain (on sale) = Sale proceeds − (cost basis per share × number of shares sold).

Practical notes on reporting:

• Employers normally include vested RSU value as wages for the year; that income affects your ordinary income tax for that year Fidelity.
• When you sell, brokers report sale proceeds; you must ensure the cost basis reported on brokerage/1099-B matches the income you reported at vesting to avoid double taxation or reporting errors Fidelity.

Worked Example

Assumptions:

• 1,000 RSUs vest on January 15, 2025.
• FMV on vest date = $25.00 per share.
• Employer withholds taxes by selling 200 of the vested shares (settling net shares received = 800).
• You later sell all 800 shares on March 1, 2026, at $40.00 per share.

Step 1 — Income recognized at vest:

• Gross value at vest = 1,000 × $25.00 = $25,000.
• That $25,000 is reported as ordinary compensation in the vesting year and forms the aggregate cost basis for the shares you ultimately receive (subject to any actual withholding adjustments by the employer).

Step 2 — Determine per-share cost basis:

• If your employer withheld 200 shares to cover taxes, you end up with 800 shares delivered to your brokerage.
• Practical allocation: the cost basis allocated to the 800 delivered shares equals the gross value associated with those shares. There are two common bookkeeping approaches: (A) treat the basis as FMV × shares actually delivered (800 × $25 = $20,000) and treat the withheld shares’ value as tax-withholding; or (B) allocate the total recognized income across all shares and adjust for the withheld portion. Either way, your net cost basis for the 800 shares you own will be $20,000 in this example (800 × $25).

Step 3 — Sale and capital gain:

• Sale proceeds = 800 × $40 = $32,000.
• Capital gain = $32,000 − $20,000 = $12,000.
• Holding period: since sale happened more than one year after the vest date (Jan 15, 2025 → Mar 1, 2026), this $12,000 would generally be treated as long-term capital gain for tax-rate purposes (holding-period rules govern this).

Interpretation: The RSU vest created ordinary income equal to the vest-date value, and later sale produced capital gain measured from that income-derived cost basis. “Profit” at sale is sale proceeds minus the cost basis Fidelity.

How to Interpret It

What the cost basis tells you:

• It separates compensation (taxed as ordinary income when RSUs vest) from investment gain/loss (taxed as capital gain or loss when shares are sold) Fidelity.
• A correct cost basis prevents double taxation: if your basis is understated, the capital-gains calculation could incorrectly show extra taxable gain; if overstated, you may underreport gains.

Key conditional points and tradeoffs:

• Liquidity vs taxation: Selling immediately at vest locks in the ordinary-income tax on the vest value and avoids future market risk. Holding shares exposes you to post-vest price movement that will create capital gains or losses measured from the vest-date basis.
• Timing matters for rates: If you expect the stock to rise and can wait more than a year, potential long-term capital gains may be taxed at lower rates than ordinary income; that is a conditional tradeoff based on risk tolerance and market expectations Fidelity.

Common misreads and fixes:

• Misread: “My brokerage reported cost basis as zero, so I don’t owe tax on the sale.” Fix: Correctly adjust your tax reporting so the vest-date income is the basis when you compute gains. (See verification checklist below.)
• Misread: “All future profit is ordinary income.” Fix: Only the value recognized at vest is ordinary income; additional gain or loss after vest is capital gain or loss measured from that basis Fidelity.