Building a completion portfolio around employer stock

You have run the math, looked at the capital gains bill on your oldest low-basis lots, and decided you are going to keep a meaningful slice of your employer stock — for now. That is a defensible choice. But the moment you make it, a second decision arrives that most people never consciously make: what should the rest of your money look like, given what you are already holding? If you keep the concentrated position and then buy the same broad index everyone else buys, you have not diversified around your bet — you have doubled it.

The 30-second answer: A completion portfolio is the rest of your holdings, built deliberately around a concentrated employer position you choose to keep, so the total portfolio resembles a balanced index rather than a doubled-down bet. Because most tech employer stock is US large-cap growth, the completion sleeve should under-weight US large-cap tech and add what is missing — value, small and mid-cap, international developed and emerging markets, and bonds, per your target allocation. The key discipline is look-through: count the employer stock's sector and factor when you measure total exposure, because a broad index fund is already roughly 30% tech. Build the tilt with new RSU proceeds and inside tax-advantaged accounts to avoid realizing gains. It manages factor overlap, not the single-name risk, so pair it with a plan to trim over time.

This guide is the keep-the-stock branch of the broader diversification playbook. It assumes you are a US resident filing a US return, that you have decided to hold a concentrated employer position for reasons you can defend, and that you now want the other 70% or 80% of your money to do the opposite of what that position already does. The aim is not to talk you out of the stock. It is to make sure the stock does not silently become your whole portfolio through the back door of buying the same thing everywhere else.

What a completion portfolio actually is, and what it is not

A completion portfolio is the set of holdings you build around a concentrated position you are keeping, sized and tilted so that the total of everything you own — the concentrated stock plus the rest — looks like a balanced, diversified portfolio rather than a leveraged bet on one sector. The word that matters is total. You stop analyzing your index funds in isolation and start analyzing the whole stack, employer stock included, as one portfolio.

Here is the honest boundary, stated up front so nothing later is misleading. A completion portfolio does not reduce the single-name risk of the shares you keep. If your employer's stock falls 55% next year, those shares fall 55%, and the completion sleeve does nothing to cushion that specific loss. What the sleeve does is narrower and still valuable: it stops you from compounding the same sector and factor bet across the rest of your money, so that a bad year for your employer is a setback rather than a wipeout. It converts "all my eggs are in one basket and I bought a second identical basket" into "I have one over-sized egg and a genuinely diversified rest."

Because of that boundary, a completion portfolio is never a reason to stop trimming. It is a way to live sanely with a concentration while you reduce it on a schedule. The two ideas work together: trim the position toward a target you can survive, and in the meantime shape everything else to offset what you still hold.

Bottom line: A completion portfolio shapes the rest of your money so the total looks balanced; it manages factor and sector overlap, not the company-specific risk of the kept shares, so it must pair with a plan to trim the position over time.

Look-through: count the stock when you measure exposure

The mistake that makes completion portfolios necessary is treating a broad index fund as automatically diversified. It is not sector-neutral. As of 2026, the information technology sector is roughly 30% or more of the S&P 500 by weight, and the largest technology and technology-adjacent companies sit at the very top of the index. If your employer is a large-cap US tech name, your "diversified" S&P 500 fund is already heavily weighted toward your own sector — and frequently holds your exact employer inside it.

Look-through analysis is the fix. Instead of measuring exposure fund by fund, you decompose every holding into its underlying sectors and factors, add the concentrated stock as its own line, and read the combined weights. Only then can you see the hidden double-up that a fund-level view hides.

Worked example. The hidden tech double-up

Take a simple two-holding portfolio: 30% in your employer (a large-cap US tech stock) and 70% in an S&P 500 index fund. On the surface it looks like "30% one stock, 70% diversified." Look through the index fund at a 30% tech weight and the picture changes.

Source	Share of portfolio	Tech weight inside it	Tech contribution
Employer stock (large-cap US tech)	30%	100%	30.0%
S&P 500 index fund	70%	~30%	21.0%
Combined technology exposure	100%	—	51.0%

The portfolio is 51% technology, not the 30% the fund-level view suggested. More than half your money rides on one sector, and your salary rides on a company inside that sector. The same arithmetic applies to the large-cap-growth factor: both the stock and the top of the index lean growth, so your factor exposure is even more lopsided than the sector number alone implies. This is the number a completion portfolio is built to correct — not by removing the 30% stock, but by making sure the other 70% under-weights tech instead of piling on more.

Bottom line: A broad index fund is already roughly 30% tech, so adding employer tech stacks the bet; measure total exposure with look-through, counting the concentrated stock as its own sector and factor line, before you design anything.

Building the sleeve: the negative image of your concentration

Once you can see the total exposure, the design rule is simple to state. The completion sleeve is the negative image of your concentration. Whatever the kept stock over-weights, the sleeve under-weights; whatever the kept stock leaves out, the sleeve adds. For the typical tech employee whose concentration is US large-cap growth, that means deliberately under-weighting US large-cap tech in the rest of the portfolio and filling in the parts of the global market that the concentrated position ignores: value, small and mid-cap, international developed, emerging markets, and bonds.

The destination is your own target allocation — a global all-equity blend, a 60/40 mix, or whatever your plan calls for. You reach it by treating the employer stock as already filling part of your US-large-cap-growth bucket and pointing the sleeve at every other bucket. Practically, that often means owning little or no additional S&P 500 in taxable, and instead reaching for total-international funds, small and mid-cap funds, value-tilted funds, and a bond allocation, so that when you add the concentrated stock back in, the whole thing lands near target.

Worked example. Filling the other 70% to reach a global all-equity target

Suppose 30% of your $600,000 investable portfolio — $180,000 — is employer large-cap US tech, and you have decided to keep it for now. You want the total to resemble a diversified global all-equity portfolio with a modest bond sleeve. Treat the $180,000 as your US-large-cap-growth bucket and build the remaining $420,000 to fill what is missing.

Sleeve holding	Target % of total	Dollars	Why it is here
Employer stock (kept)	30%	$180,000	The concentration you are keeping; counts as US large-cap growth
US value / total US ex-tech tilt	15%	$90,000	Adds the value factor the stock lacks
US small and mid-cap	10%	$60,000	Adds the size factor the stock lacks
International developed	18%	$108,000	Adds non-US exposure entirely absent from the stock
Emerging markets	7%	$42,000	Adds the highest-growth markets the stock ignores
Bonds (total bond / Treasuries)	20%	$120,000	Adds the asset class with the lowest correlation to your stock
Total	100%	$600,000	Looks like a balanced global portfolio, not a tech bet

Notice what is absent: there is little or no plain S&P 500 fund in the sleeve, precisely because the kept stock and any S&P 500 holding would stack the same large-cap tech exposure. With this sleeve, your look-through technology weight drops from the 51% of the earlier example toward the low 30s — close to the market's own weight rather than far above it. The single-stock risk on the $180,000 is unchanged; the portfolio around it is no longer amplifying the same bet.

Bottom line: Design the sleeve as the negative image of the concentration — under-weight US large-cap tech, add value, size, international, emerging markets, and bonds — and reach your own target allocation by treating the kept stock as already filling the large-cap-growth bucket.

Tilting without a tax bill: use new money, not old gains

The catch with building a completion portfolio is that the most natural way to do it — sell some of your existing index funds and buy the under-weight asset classes — realizes capital gains in a taxable account. Long-term gains are taxed at 0%, 15%, or 20% depending on income, plus the 3.8% NIIT above $200,000 single or $250,000 married MAGI. Churning a taxable portfolio to fix factor tilts can cost more in tax than the tilt is worth.

The cheaper path is to tilt with flows rather than with stock. Two levers do most of the work. First, direct every new dollar — RSU vest proceeds, paycheck contributions, bonus, and reinvested dividends — at the asset classes you are under-weight, so the portfolio drifts toward target without any selling. Second, place the highest-turnover or least tax-efficient parts of the tilt inside tax-advantaged accounts, where trades and rebalances are tax-free. Bonds and any actively traded value or factor strategy belong in the 401(k) or Roth IRA; the buy-and-hold equity index belongs in taxable. The interplay of which asset goes where is its own discipline — see asset location for tax-efficient investing — but the headline is that you can do most of a completion tilt without realizing a single dollar of gain.

Worked example. A year of vests redirected toward the under-weight sleeve

Take an engineer who vests $15,000 of employer stock each quarter and contributes $1,500 a month to a brokerage account, and who is starting over-weight US large-cap tech and under-weight everything else. Rather than selling appreciated funds, every new dollar over the year is pointed at the gaps.

Source of new money	Annual dollars	Directed to	Effect
RSU vest proceeds (sold at vest, ~$0 gain)	$60,000	International, EM, value, small-cap	Adds the missing equity factors with no embedded gain
Taxable contributions ($1,500/mo)	$18,000	Bonds and international	Builds the low-correlation sleeve
401(k) contributions	$23,000	Bonds and total-market, rebalanced free	Tax-free tilting inside the wrapper
Total new money deployed	$101,000	Under-weight asset classes	Portfolio moves toward target

Selling RSUs at vest is the quiet hero here: because basis resets to the vest-date price, a same-day sale realizes essentially no capital gain, so $60,000 of fresh, tax-neutral cash is available each year to fill the sleeve. On a $600,000 portfolio, deploying roughly $101,000 of new money over a year toward the under-weight buckets moves the allocation meaningfully toward target without realizing a cent of gain on existing holdings. Do this for two or three years and the completion portfolio largely builds itself.

Bottom line: Tilt with flows, not with old gains — point new RSU proceeds and contributions at the under-weight asset classes and put the least tax-efficient tilts inside tax-advantaged accounts, so the completion portfolio assembles itself without a capital gains bill.

The completion portfolio is a bridge, not a destination

It is tempting to treat a well-built completion portfolio as the end of the job — the concentration is balanced, so why keep selling? The answer goes back to the honest boundary. The sleeve manages overlap; it does nothing about the single-name risk on the kept shares. A 55% drawdown in one stock that is 30% of your net worth is still a 16.5% hit to your whole portfolio at the same moment your bonus shrinks and your job is least secure. Balance around the position does not change that arithmetic.

So the completion portfolio should run alongside a deliberate trim. As you sell down the concentrated stock over time — using long-term lots, spreading sales across tax years, harvesting losses to offset gains, and timing larger sales for lower-income years — you redeploy the proceeds into the same under-weight sleeve. The two processes reinforce each other: each trim both reduces single-name risk and funds the diversification you already designed. Over several years the concentrated position shrinks toward a size you can survive in any market, and the completion sleeve grows into a genuinely diversified core. Tools like a 10b5-1 plan for insiders, an exchange fund for very large low-basis stakes, or direct indexing to harvest offsetting losses can make that trim cheaper and more disciplined.

Bottom line: Treat the completion portfolio as a bridge that keeps you balanced while you reduce the concentration, never as a reason to stop trimming — pair it with a scheduled sell-down so single-name risk falls as overlap risk is managed.

How big a concentration is worth completing around at all

A completion portfolio is the right tool when you have a real reason to keep the stock and the position is large enough that selling it all at once is costly. It is the wrong tool when the position is small, when the gains are trivial, or when the only reason you are holding is inertia. There is no point engineering a sleeve to offset a 5% position that you could sell tomorrow for almost no tax.

The rough thresholds most advisers use are a useful guide. A single stock above 10% to 15% of liquid net worth is a concentration worth managing deliberately, and above 20% to 25% it is a bet you should have a strong, specific reason to keep. If you are below the lower line, the honest answer is usually to sell down rather than build elaborate machinery around a position that barely moves the portfolio. The full framework for sizing the position lives in how much employer stock is too much. The completion portfolio earns its keep in the middle and upper range — positions large enough that an immediate full sale would trigger a painful gain, where keeping some while balancing the rest is a reasonable compromise.

Bottom line: Build a completion portfolio only when the position is large enough that a clean sale is costly and you have a real reason to keep it; below roughly 10% of liquid net worth, the simpler answer is usually to sell down rather than engineer around it.

Common mistakes

• Counting your index fund as diversified without look-through. A broad fund is already roughly 30% tech; if you skip the look-through step you will under-count your real concentration by half.
• Adding an S&P 500 fund to the sleeve. The kept stock and an S&P 500 holding stack the same large-cap tech bet. Reach for the under-weight buckets instead.
• Rebalancing the tilt in taxable and eating the gains. Use new RSU proceeds and tax-advantaged accounts first; only sell appreciated taxable lots when flows cannot do the job.
• Believing the sleeve protects the kept shares. It does not. It manages overlap, not single-name risk. If you forget this, you will hold too much for too long.
• Treating the completion portfolio as the end of the job. It is a bridge. Without a scheduled trim, you are still carrying a concentration that can crater your net worth in a bad year.
• Forgetting NIIT when you do sell. Above $200,000 single or $250,000 married MAGI, add 3.8% to your capital gains rate when you model any unwind.

The closing read

A completion portfolio is the grown-up version of "I'm keeping the stock." It accepts the choice you have made and then refuses to let that one choice quietly become your entire allocation. The discipline is two ideas held at once: look through everything you own — the index funds and the employer shares together — to see your real sector and factor weights, then build the rest of the portfolio as the negative image of the concentration, funded with new money rather than realized gains. What it cannot do is rescue you from the single stock itself. The shares you keep can still fall hard, all at once, in the same year your job feels least safe. So the completion sleeve is the thing you build while you trim, not instead of trimming. Get both right and you keep the upside you believe in without betting the house on it twice.

Cross-references

• What to do with vested RSUs: the diversification playbook
• How much employer stock is too much?
• Direct indexing around a concentrated employer position
• Exchange funds and swap funds for concentrated stock
• Rule 10b5-1 plans for selling company stock
• Asset location for tax-efficient investing
• Turning RSUs into a retirement corpus: 401(k) and Roth
• The RSU tax-saving playbook: harvesting, NUA, and DAFs
• Funding life goals with RSUs: house, 529, and goal-based selling
• Should you sell RSUs at vest or hold?
• US residents with US RSUs: the complete guide
• What is an RSU? Restricted Stock Units explained

Critical disclaimer: this article reflects US federal tax rules and capital-markets practice as of June 2026 and is general information, not personalised advice. Capital gains rates, NIIT thresholds, sector weights in major indices, and the tax treatment of rebalancing and asset location can change and depend on your specific facts, state of residence, income, and insider status. A completion portfolio manages factor and sector overlap; it does not reduce the company-specific risk of any concentrated position you keep. It does not substitute for advice from a licensed CPA, CFP, or securities-law counsel. Nothing here is a recommendation to buy or sell any specific security.