The Tax Trap in RSU Vesting, and How to Plan for It

I work with tech executives whose RSUs vest in large, uneven blocks. The same surprise comes up every year. The good news: the entire problem is predictable, which means you can plan for it before the shares hit your account instead of reacting after.

How are RSUs taxed when they vest?

RSUs are taxed as ordinary income at vest. When a block vests, the fair market value of those shares becomes W-2 wages that year, taxed at your ordinary income rate. This happens whether you sell the shares or hold every one of them.

Your cost basis in the shares is set to that vest-date value. So a later sale only creates a capital gain or loss on the change in price after vesting. If you sell right at vest, there is usually little or no additional tax, because your basis equals the value you were already taxed on. The IRS treats the vest itself as the taxable event, following the same supplemental wage rules the agency lays out in IRS Publication 15.

The trap is not the tax rate. It is the timing and the withholding, which is where the next section comes in.

Why does 22% withholding leave you with an April tax bill?

Most companies withhold federal tax on RSUs at the flat 22% supplemental wage rate. If your marginal rate is 37%, that 22% withholds far less than you actually owe. The difference does not disappear. It becomes a balance due when you file.

That is the core of the trap. You are taxed at 37% on the vested value, but only 22% was set aside for you. The other 15 points are yours to cover, often on shares you chose to hold rather than sell. The bill arrives for income that never passed through your checking account.

What does the withholding gap look like on $400k of RSUs?

Here is an illustrative example. Assume $400,000 of RSUs vest in a single year for someone already in the top bracket.

• Withheld at 22%: about $88,000
• Actual federal tax at top marginal rates: closer to $148,000
• Gap before state tax: roughly $60,000

These figures are illustrative and rate-dependent. They assume the vested value stacks on top of other income at top marginal rates, and they exclude state income tax and the additional Medicare surtax, both of which would widen the gap further. Your real number depends on your full income picture.

Hypothetical illustration only, not a projection of actual results. Figures assume the stated inputs and returns, which are not guaranteed; your outcome depends on your contributions, investment returns, tax rates, and time horizon. Past performance does not guarantee future results.

A $60,000 gap is not a rounding error. It is a planned-for line item or an unwelcome shock, and the only difference between the two is whether you ran the number in advance. You can run your exact numbers using the free INSTANT results calculator on advisorjay.com.

Once your RSUs vest, holding is a decision

The day your RSUs vest, you have already paid ordinary income tax on them. From that point, holding the shares is an active choice, the same as taking that after-tax cash and buying company stock with it.

That reframe is the useful one. Ask the plain question: would you buy this much of your own company today, with cash, at today's price? If the honest answer is no, then holding a large vested position is a decision worth revisiting.

Concentration is the risk here. Your salary, your bonus, your future vests, and often your stock option upside are already tied to one company. A large vested share balance stacks more of your net worth on the same single outcome. Diversifying is not disloyalty. It is separating your career from your portfolio so one bad year does not damage both at once.

How do you fund the tax on purpose?

Fund the tax deliberately rather than discovering it in April. There are three common ways, and they are not mutually exclusive.

1. Estimate the real liability at vest. Calculate the tax at your marginal rate on the vested value, not the 22% withheld, and know the gap the day the shares land.
2. Set the money aside or pay quarterly estimates. If you hold the shares, reserve the gap in cash or send quarterly estimated payments so you are not carrying an underpayment penalty into April.
3. Use sell-to-cover. Selling a portion of each vesting block to cover the tax solves two problems at once. It funds the liability and trims the concentrated position in the same move.

Run this past your CPA or tax team before you act. Your state, your other income, and any prior-year safe-harbor rules change how much you should set aside and whether quarterly estimates make sense.

What offsets help in a big vesting year?

In a year with an unusually large vest, some general strategies can reduce the sting. These are educational, not recommendations, and the right mix depends entirely on your situation.

• Charitable timing. If you already give, concentrating several years of giving into a high-income year, sometimes through a donor advised fund, can align a larger deduction with the year you need it most.
• Loss harvesting. Realized losses elsewhere in your taxable accounts may offset gains and, within limits, a portion of ordinary income.
• Asset location. Placing tax-inefficient holdings in tax-advantaged accounts can reduce the ongoing drag on a larger, more concentrated portfolio.
• Strategies structured to offset ordinary income. In large years, some approaches are designed to create deductions or offsets against ordinary income. Whether any of them fit depends on your facts, your risk tolerance, and your tax team's read.

None of these are guaranteed outcomes, and none should be chosen for the tax benefit alone. This is exactly the territory to work through with your CPA or tax advisor, because the details determine whether a strategy helps you or simply adds complexity.

A five-step framework for RSU vesting

Run every vest through the same five steps and the trap stops being a surprise.

1. Know the real number. Calculate the actual tax on the vested value at your marginal rate, not the 22% withheld.
2. Decide on the shares deliberately. Apply the "would I buy this much today, with cash?" test to each vested block.
3. Fund the tax on purpose. Set aside the gap, pay quarterly estimates, or sell-to-cover.
4. Look at offsets. In a large year, review charitable timing, loss harvesting, and asset location with your tax team.
5. Run it as a system. Vesting repeats. Build a repeatable process instead of reacting each April.

Frequently asked questions

Are RSUs taxed twice?

No. There are two separate events, not double taxation. You pay ordinary income tax on the value at vest, then capital gains tax only on any increase in price if you sell later. Sell at vest and there is usually little or no additional tax.

Why do I owe taxes on RSUs I did not sell?

Because vesting is the taxable event, not selling. The full vested value is W-2 income the year it vests, whether you hold the shares or not. Withholding at 22% often does not cover the full liability for high earners.

How much should I set aside for RSU taxes?

Plan closer to your marginal rate than the 22% that was withheld. In the top bracket the difference can be large, as the illustrative example above shows. Your exact figure depends on your total income and state.

Does selling RSUs right at vest create more tax?

Usually very little. Your cost basis equals the vest-date value, so selling immediately produces almost no additional gain. Sell-to-cover uses this to fund the tax and reduce concentration at the same time.