The Situation

Andre is a senior engineer at Datadog, about five years in, living in Austin. This spring a big chunk of his RSUs vested — roughly $240,000 worth in the first half of the year — the reward for a stretch of very good work and a rising stock price. When the shares hit his account, he saw taxes had already been taken out. So he did what most people do: he assumed payroll had handled it and moved on.

He wasn't being careless. He maxes his 401(k), he has a CPA who files a clean return every April, and he'd never had a tax problem in his life. From where he sat, the system was working exactly the way it was supposed to.

The Gap We Found

Here's the thing almost no one is told: when RSUs vest, employers withhold federal tax at the flat 22% "supplemental" rate. But Andre's income puts him in the 35% federal marginal bracket. On a $240,000 vest, that 13-point gap is about $32,000 in tax that was never withheld — and it wouldn't have shown up anywhere until he filed next April. His CPA is excellent, but a CPA sees the year after it's over. His payroll system did exactly what payroll systems do. Nobody was watching the space between the two — which is precisely where the shortfall lived.

What We Did

The first thing our AI agents did was parse Andre's actual payroll and vesting data and lay the real numbers side by side: taxes already withheld versus taxes actually owed for the year. That's what surfaced the ~$32,000 gap in minutes — not in April. Because it was still July, we had options that simply don't exist in the spring.

We ran the safe-harbor math with him. High earners generally avoid an IRS underpayment penalty if they pay in at least 110% of last year's tax or 90% of this year's — so we calculated the exact number he needed to reach and built a plan to get there. Rather than lean entirely on a lump-sum estimated payment, we bumped his W-4 withholding for the second half of the year. Withholding is treated by the IRS as if it were paid evenly across the whole year, so increasing it now retroactively cures the earlier shortfall — and we layered in a right-sized Q3 estimated payment (due September 15) to close the rest. His advisor and our system will track it through the deadline so nothing slips.

While we were in there, we flagged something else: Andre had been letting every vested share ride, and Datadog stock had quietly grown to about 30% of his net worth. We set a simple rule going forward — sell at vest, when there's little to no gain to tax — and redirect the proceeds into a diversified portfolio. It turns a future concentration problem into a non-event, on autopilot.

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The Result

• ~$32,000 tax shortfall caught in July instead of discovered as a painful surprise at filing — with months of runway to fix it calmly.
• Underpayment penalty avoided by hitting the safe-harbor threshold through a combination of adjusted withholding and a single Q3 estimated payment.
• Concentration risk addressed — a standing sell-at-vest plan brings a 30%-of-net-worth position back toward a healthy allocation over time.
• Peace of mind — Andre goes into next April knowing the number, instead of dreading it.

Why This Worked

None of Andre's advisors failed him — his CPA, his payroll, his 401(k) were all doing their jobs. What was missing was someone looking at all of it at once, in real time, while there was still time to act. That's the whole idea behind Alphanso: a flat fee, a fiduciary team, and AI agents that watch the gaps between your paycheck, your equity, and your tax bill so a mid-year fix stays a mid-year fix — not a spring disaster. If you took a big vest this year and you're not sure whether your withholding actually covered it, the window to check is open right now. We'd love to walk you through it: alphanso.ai/request-a-callback.

Disclosure

This case study is a composite illustration based on real Alphanso client scenarios. Names and identifying details have been changed for privacy. Results are not guaranteed and will vary based on individual circumstances. All investing involves risk, including the possible loss of principal. Alphanso LLC is a registered investment adviser.