Why Holding RSUs After They Vest Creates a Second Tax Bill (and What to Do About It)

She's a senior director of product at a public tech company. Eight years in. The RSUs that felt like a bonus early on have stacked into about $2.4 million of one stock. She knows her company withholds 22% when each grant vests, and she has learned the hard way what that gap costs in April. So she planned for it. Extra estimated payments, more withholding elected. What she hasn't thought about is the second tax bill. The capital gains she'll owe on the appreciation between the vest price and the sale price, whenever she finally sells.

That second bill is what this post is about. The difference between what you sell your RSU shares for and the cost basis set at vesting is a capital gain, and it gets taxed separately from the ordinary income you already paid. Many executives plan for the first tax event and miss the second one entirely.

The tax event you already know about

When your RSUs vest, the IRS treats the value as ordinary income. Your company reports it on your W-2, and it's taxed at your marginal rate, up to 37%, plus the 3.8% Net Investment Income Tax if your income is high enough. The default federal withholding is 22%, which is almost certainly not enough for a senior tech executive in the top brackets. That gap is the April surprise most people eventually learn to plan for.

But here's what's easy to miss: that first tax bill is not the end of the story. It's only the beginning.

Now you own shares with a cost basis

When your RSUs vest, the shares land in your brokerage account and a cost basis is set. The cost basis equals the market price of the stock on the vest date. If your company uses sell-to-cover, some shares are sold to cover the withholding, and the remaining shares enter your account with that same cost basis.

If you sell those shares the same day they vest, the sale price matches the vest price and there is no gain. The full amount is already captured as ordinary income on your W-2. That is the cleanest outcome from a tax perspective.

But if you hold. If you watch the stock climb and decide to let it ride, the cost basis stays fixed at the vest price. And everything above that price becomes a capital gain whenever you eventually sell. We've written before about how cost basis determines the tax bill when you sell, and the same principle applies here.

The second tax bill: capital gains

The difference between what you sell your RSU shares for and their cost basis is a capital gain. How it's taxed depends on how long you held.

If you sell within one year of the vest date, it's a short-term capital gain, taxed at your ordinary income rate, up to 37%.

If you hold for more than one year, it qualifies as a long-term capital gain, which gets a preferential rate. For most high earners, that's 20%, plus the 3.8% NIIT, for a combined 23.8%. That is a meaningful difference compared to 37% on short-term gains, but it is still a real tax bill.

Here's how the mechanics work in a representative scenario: say shares vest when the stock is at $100, giving them a cost basis of $100. You hold them for two years and the stock climbs to $180. When you sell, the $80 per share difference is a long-term capital gain. On 10,000 shares, that is $800,000 in gain, with roughly $190,000 in federal tax at the 23.8% rate, plus any state tax.

That is the second tax bill. And it's easy to miss because it doesn't show up on your W-2. It shows up on your brokerage's 1099-B the year you sell.

Holding means the tax bill grows with the stock

The catch-22 of holding RSUs after vesting is that the longer you hold, the more the stock can appreciate, and the larger the capital gains tax bill becomes. The same behavior that built your net worth can quietly grow a future liability you haven't budgeted for.

There is also the hidden cost of inaction. If your company stock keeps climbing, the tax bill keeps growing, and the decision to sell gets harder, not easier. What started as a manageable tax event can become a reason to keep holding, even when diversification would be the smarter move. We've written before about how a multi-year diversification plan can help you unwind a concentrated position on your terms.

The fork in the road

When your RSUs vest, you have a choice. You don't have to make it in the moment, but you should make it intentionally with the end in mind.

Sell the same day. The simplest path. The full value is ordinary income. No capital gains issue. You pay the tax, pocket the rest, and your concentration doesn't grow.

Sell a portion. Cover the tax bill and take some diversification. Let the rest ride with a plan to sell over time. The key is having a plan, not just a hope.

Hold and plan. If you believe in the stock and want to hold, understand the capital gains exposure you're building. Set a target for when you'll sell and revisit it annually. A 10b5-1 plan can help you execute without the emotional weight of timing the market, as we've covered in our post on 10b5-1 planning.

The wrong answer is holding without thinking about it. The RSUs that vest this quarter will create two tax events: the one you see on your W-2 and the one you won't see until you sell. Planning for both, before the end of the year, is what turns tax compliance into tax strategy.

Most firms file your return and move on. A strategist helps you see both tax bills, not just the first one. If you'd like to talk through your RSU situation and build a plan that accounts for both the vesting tax and the eventual sale, book a free 15-minute discovery call with us. Call (619) 280-2700 or email info@RoadmapTax.com.

FAQ

When do I pay capital gains tax on RSU shares?

You pay capital gains tax in the year you sell the shares, not when they vest. The gain is the difference between your sale price and the cost basis set at vesting.

What is the cost basis on my RSU shares?

The cost basis is the market price of the stock on the vest date. Your brokerage reports this on your 1099-B when you sell. It is the starting point for calculating your capital gain.

Do I pay capital gains if I sell RSUs the same day they vest?

No. If you sell the same day, the sale price matches the vest price, so there is no gain. The full value is already taxed as ordinary income on your W-2.

What's the difference between short-term and long-term capital gains on RSUs?

Short-term gains apply to shares held less than one year after vesting and are taxed at your ordinary income rate, up to 37%. Long-term gains apply to shares held more than one year and are taxed at preferential rates, typically 20% plus the 3.8% NIIT for high earners.

How do I know if I should hold or sell my vested RSUs?

There is no single answer. The decision depends on your concentration, your tax bracket, your holding period, your financial goals, and your confidence in the stock. A tax strategist can help you work through the trade-offs with a concrete plan.