How to Read Your Pay Stub When You Have RSUs, ESPPs, and Bonuses

Why Tech Pay Stubs Are Different

A standard W2 employee sees base salary, federal and state withholding, Social Security, Medicare, and maybe a 401(k) deduction. Straightforward. A tech employee with equity compensation sees all of that plus RSU vest income, shares sold to cover taxes, ESPP payroll deductions, ESPP purchase income, supplemental withholding at a flat rate, and bonus income withheld at yet another rate. All on the same stub, sometimes in the same pay period.

The result is a document that looks nothing like what most personal finance advice prepares you for. If you do not understand each line item, you will almost certainly misestimate your actual tax liability, misunderstand your net compensation, or both.

RSU Vest Line Items: What Actually Happens on Vest Day

When RSUs vest, three things happen simultaneously on your pay stub:

• Gross RSU income appears as ordinary income, equal to the number of shares vesting multiplied by the fair market value on the vest date
• Shares sold to cover appears as a tax withholding mechanism, where your employer automatically sells a portion of the vesting shares to cover federal, state, Social Security, and Medicare taxes
• Net shares deposited is what actually lands in your brokerage account after the sell to cover

A Concrete Example

You have 100 RSUs vesting when your company's stock is at $180 per share.

• Gross income: 100 shares x $180 = $18,000 added to your W2 wages for this pay period
• Shares sold to cover: approximately 40 shares sold at $180 = $7,200 withheld for taxes (federal supplemental at 22%, state, Social Security, Medicare)
• Net shares deposited: 60 shares land in your Fidelity, Schwab, or Morgan Stanley account

The critical point: the sell to cover is not a voluntary sale you chose to make. It is automatic payroll tax withholding. Your employer sells shares on your behalf to remit taxes, exactly the same way they withhold cash from your salary. But here is the problem: the amount withheld through sell to cover is almost never enough.

The Supplemental Withholding Rate: Why You Owe Money Every April

RSU vests and bonuses are classified as supplemental wages by the IRS. Employers are required to withhold at one of two rates:

• 22% on the first $1 million of supplemental wages in a calendar year
• 37% on supplemental wages exceeding $1 million

Most tech employees fall into the 22% bucket. But if your total taxable income puts you in the 32%, 35%, or 37% federal bracket, the 22% withholding leaves a significant gap.

The Math That Creates Tax Day Surprises

An engineer earning $200,000 in base salary with $120,000 in RSU vests has total income of $320,000. Their marginal federal rate on that income is 32%. But the RSU vests were only withheld at 22%. That is a 10 percentage point gap on $120,000, meaning approximately $12,000 in additional federal tax owed at filing time, before even considering state taxes.

Add California's 9.3% to 12.3% bracket on the same income and the total underwithholding can easily reach $18,000 to $22,000. This is the single most common reason tech employees owe large amounts at tax time. It is not a mistake on your pay stub. It is how supplemental withholding works by design.

What to do: adjust your W4 to withhold additional dollars per pay period, or make quarterly estimated tax payments (Form 1040ES) starting in the quarter your first large vest hits.

ESPP Line Items: Deductions Are Not Taxes

Your ESPP creates two distinct line items on your pay stub, and confusing them is a costly mistake.

The Payroll Deduction

Each pay period, a percentage of your salary (typically 1% to 15%) is deducted and held in an accumulation account. This line item appears as a post tax deduction, not a tax. Your full salary is still taxed as normal; the ESPP deduction is taken from your net pay. It is savings, not withholding.

The Purchase Event

At the end of each offering period (typically every six months), accumulated funds purchase shares at a discount (usually 15% off the lower of the enrollment date price or purchase date price). The discount portion becomes taxable income, but when it becomes taxable depends on how long you hold the shares:

• Disqualifying disposition (sold within two years of enrollment or one year of purchase): the discount is taxed as ordinary income in the year of sale, and it will appear on your W2
• Qualifying disposition (held beyond both thresholds): a portion of the gain is taxed as ordinary income and the remainder as long term capital gains

For most tech employees with concentrated equity risk, selling immediately (a disqualifying disposition) and capturing the guaranteed discount is the correct move. Do not let the tax tail wag the diversification dog.

The Social Security Wage Base: Your Mid Year Raise

Social Security tax (6.2% employee share) applies only to wages up to the wage base, which is $176,100 in 2026. Once your year to date earnings cross that threshold, Social Security withholding drops to zero. Medicare (1.45%) continues with no cap, and the Additional Medicare Tax (0.9%) kicks in above $200,000 for single filers.

For a tech employee earning $220,000 in base salary, Social Security tax stops around late September or early October. That means your net paycheck increases by roughly $500 to $600 per pay period for the remainder of the year.

Do not spend this increase. It is not a raise. It is a temporary reduction in withholding that resets to full deductions on January 1. Redirect the extra cash to estimated tax payments, your emergency fund, or taxable brokerage contributions.

Sample Pay Stub: RSU Vest Month

Here is what a February pay stub might look like for a senior engineer who receives both regular salary and an RSU vest in the same period:

Notice that the RSU vest added $29,250 to gross income but you received zero additional cash. The entire RSU amount was consumed by sell to cover withholding. Your cash deposit is derived almost entirely from your base salary. This is normal. The 60% of shares that were not sold to cover are sitting in your brokerage account as stock, not cash.

Using Year to Date Totals to Catch Problems Early

Your YTD section is the most important part of your pay stub for tax planning. Every pay period, check three numbers:

• YTD gross income: multiply this by 12 and divide by the current month number to project your annual income. Compare to last year. If it is significantly higher (common in years with large vest schedules), you likely need to increase withholding.
• YTD federal tax withheld: divide by YTD gross income to get your effective withholding rate. If this rate is below 28% and your total income will exceed $300,000, you are almost certainly underwithheld.
• YTD Social Security wages: track how close you are to the $176,100 wage base. Once you cross it, redirect the Social Security savings to cover your withholding gap.

Run this check quarterly at minimum. A five minute review in March can prevent a $15,000 surprise in April of the following year.

Common Mistakes That Cost Tech Employees Thousands

Assuming Sell to Cover Equals Your Full Tax Bill

The sell to cover withholding on RSU vests covers approximately 35% to 42% of the gross value (combining federal supplemental, state, Social Security, and Medicare). For employees in the 32% or higher federal bracket, the true combined rate is closer to 45% to 50% in states like California or New York. The gap between what was withheld and what you owe accumulates silently throughout the year.

Not Tracking RSU Cost Basis

When RSUs vest, the fair market value on the vest date becomes your cost basis for capital gains purposes. If your broker reports the cost basis incorrectly (or reports it as $0), you will be taxed again on income you already paid tax on through the vest. Verify that your 1099B reflects the correct cost basis for every lot of RSU shares you sell.

Confusing ESPP Deductions with Tax Withholding

ESPP payroll deductions reduce your net pay but they are not tax payments. They are after tax savings being accumulated to purchase stock. If you look at your total deductions line and mentally count the ESPP amount as "taxes paid," you will overestimate your withholding and underestimate what you owe.

Ignoring State Tax on RSU Vests

Some employers withhold state tax on RSU vests at a flat rate that may not match your actual state bracket. In California, supplemental state withholding is 10.23%, but your marginal state rate could be 12.3% (plus the 1% Mental Health Services Tax above $1 million). Check that state withholding on equity income aligns with your actual bracket.

The Bottom Line

Your pay stub is the earliest signal of whether your tax withholding strategy is working or failing. Do not wait until you file your return to discover a five figure shortfall. Read the stub every pay period where equity income appears, project your annual liability from the YTD totals, and adjust withholding or estimated payments proactively. The thirty minutes you spend understanding these line items will save you thousands in penalties, interest, and tax day stress.