Secondary Sale of Private Stock: Tax and Process

A $2,000,000 secondary sale of private company stock — long-term, seller resident in California — nets roughly $1,218,000 after federal long-term capital gains tax, the net investment income tax, California income tax, and advisory and legal fees. That is a Finluxy Liquidity Event Net Yield of 60.9%. Move the same seller to Texas before the closing and the net jumps past $1,510,000. The stock is identical. The spread is entirely tax geography and process structure.

Secondary sales — pre-IPO stock transactions where an existing shareholder sells to a buyer rather than the company issuing new shares — have become the dominant liquidity path for employees and founders at companies that stay private for a decade or more. The math is unforgiving in a way most coverage skips: the headline number is gross proceeds, and the gap between gross proceeds and net proceeds routinely runs 20 to 40 cents on the dollar depending on holding period and state. This analysis breaks down each component, calculates the net yield across scenarios, and corrects a widely repeated error about how California taxes these gains for sellers who have left the state.

The numbers at a glance

Five figures define the economics of a secondary sale for a top-bracket seller. Every downstream calculation in this article traces back to them.

Sources: IRS Topic 409 and Rev. Proc. 2024-40 (federal LTCG, 2025); IRS Topic 559 / IRC §1411 (NIIT); California FTB / Revenue & Taxation Code (CA top rate, 2025). Combined rate assumes seller above all thresholds.

Why holding period decides almost everything

Start with the single variable that swings the outcome most: how long you held the stock before selling. The liquidity event tax treatment by type hinges on this distinction, and a secondary sale is the cleanest case to see it in isolation.

If you held the shares more than one year, the gain is LTCG, taxed federally at 0%, 15%, or 20% depending on taxable income. For 2025, the 20% federal rate applies once taxable income exceeds the top long-term capital gains threshold — $533,400 for single filers and $600,050 for married filing jointly. A seven-figure secondary sale clears that ceiling on its own. Hold the shares one year or less and the gain is STCG, taxed as ordinary income at federal rates up to 37%. A stock sold on day 365 is short-term; day 366 is long-term — and that one day is worth 17 federal percentage points at the top.

On top of either rate sits the NIIT. The Net Investment Income Tax applies a 3.8% rate to certain net investment income of individuals with modified adjusted gross income above the statutory threshold, which is $250,000 for married filing jointly and $200,000 for single filers in 2025. Capital gains are net investment income. A large secondary sale pushes MAGI far past those lines, so for practical purposes the full gain carries the surtax. One detail most sellers miss: these thresholds are not adjusted for inflation, so more taxpayers fall into NIIT territory every year even when real income is flat.

Building the net proceeds waterfall

Gross proceeds is where every projection starts and where most stop. The net proceeds figure is what actually reaches the seller’s account. Walk a $2,000,000 LTCG secondary sale by a California resident through the full waterfall, assuming negligible basis (early exercise or founder stock at par), so nearly the entire amount is gain.

Sources: IRS (federal LTCG 20%, NIIT 3.8%, 2025); California FTB (13.3% top rate, 2025). Fee estimate reflects typical secondary-sale legal review plus advisory engagement; actual fees vary. Basis assumed negligible for illustration.

Combined tax of 37.1% comes to $742,000. Add $40,000 in legal and advisory cost and total leakage is $782,000. Net proceeds: $1,218,000. The California tax on liquidity events is the largest single swing factor after the federal rate, and unlike the federal system, California offers no preferential treatment for long holds.

California is the expensive outlier for a specific structural reason. California taxes all capital gains as ordinary income, with no reduced rate for assets held longer than one year. The state’s top rate reaches 13.3%, which includes a 1% Mental Health Services Tax surcharge on income above $1 million. There is no California analog to the federal 0/15/20 schedule — a one-day-old gain and a ten-year-old gain are taxed identically at the state level.

The Finluxy Liquidity Event Net Yield, scenario by scenario

Net yield — net after-tax, after-fee proceeds divided by gross pre-tax proceeds, expressed as a percentage — is the single number that lets you compare a secondary sale across holding periods and states without re-running the whole waterfall each time. Here it is for four scenarios on the same $2,000,000 gross.

Sources: IRS (federal LTCG 20%, ordinary top 37%, NIIT 3.8%, 2025); California FTB (13.3%, 2025); Texas has no state income tax. STCG modeled at 37% federal + 3.8% NIIT. Fees held at $40,000 across scenarios. Net yield = net proceeds ÷ gross proceeds × 100.

The range is stark. The best case here — long-term hold, no-income-tax state — yields 74.2%. The worst — short-term hold in California — yields 47.7%. That 26.5-point spread on identical gross proceeds is $530,000. Holding period and residency, two variables the seller often controls, account for nearly all of it. The $2M liquidity event net yield by state comparison shows the state dimension across more jurisdictions; the holding-period dimension is captured in the lockup period cost analysis for post-IPO sellers facing the same one-year clock.

The California sourcing error worth correcting

Here is what most secondary-sale coverage gets wrong, and where the dataset points the other way. A common claim is that California taxes the gain on a secondary sale of a California company’s stock even after the seller has moved out of state — that the company’s California location “follows” the gain. For a sale of stock as intangible property, that is not how California sources the capital gain.

California’s own guidance is explicit. When a former resident disposes of stock while a nonresident, the income is characterized as gain from the sale of intangible personal property having a source in the seller’s state of residence at the time of sale. The Franchise Tax Board’s nonresident publication reinforces it: installment gains from the sale of intangible property are generally sourced to the recipient’s state of residence at the time of the sale. Case law backs the rule — capital gains from a nonresident’s sale of stock in a California-based corporation are treated as the sale of intangible property, not taxed by California, because the gain is sourced to the seller’s residence.

What California does tax for a former resident is the compensation element of equity, not the capital gain on the stock. If you exercise nonstatutory options or vest RSUs while performing services in California, California taxes the ordinary-income portion attributable to those California-performed services even after you move — but the capital appreciation above the value at vesting or exercise is sourced to your new state. The distinction is the entire ballgame for someone who moved from San Francisco to Austin before selling. The ordinary-income wage piece earned in California stays California-taxable; the post-vest stock appreciation sold as a nonresident does not. Treating the whole secondary-sale gain as California-source overstates the tax for a genuine nonresident, sometimes by six figures. The aggressive FTB sourcing positions that do exist apply to partnership interests with California business situs and “hot asset” recharacterization — narrow fact patterns, not the typical employee selling common stock.

This matters for planning because it means the state line, not the company’s headquarters, governs the capital gain. The tax-efficient diversification path after a windfall looks very different once you know the gain follows your residency rather than the cap table.

Process: how a secondary sale actually closes

Tax is half the picture. The mechanics of getting from offer to wire transfer carry their own friction and cost. A secondary sale is not an open-market trade — there is no exchange, no instant liquidity, and the company sits in the middle of every transaction.

Most private companies impose a right of first refusal and a transfer-approval requirement in their bylaws or shareholder agreements. The seller must notify the company, which can match the buyer’s price or block the transfer outright. Many companies route all secondary activity through a single sanctioned channel — a tender offer the company organizes, or an approved platform — and prohibit off-platform sales entirely. That control is why a tender offer versus open-market sale comparison is the right frame for private stock: for pre-IPO shares, the company-run tender is frequently the only path available, and its price is set by the company and lead investors, not by a market.

Legal and advisory fees in the waterfall above cover the real work this generates: reviewing transfer restrictions, confirming the buyer qualifies under securities exemptions, handling the company’s ROFR process, and structuring the seller’s tax position. For sellers still inside the company who want to sell on a schedule rather than all at once, a 10b5-1 plan setup for pre-IPO sellers can pre-commit sales and insulate against insider-trading exposure, though those plans matter most as a public listing approaches.

What the $150k+ household should weigh

For a household already earning $150k+ in ordinary income, a secondary sale lands entirely in the top tax strata — there is no low-bracket room left to absorb any of the gain. That fact reframes the decisions. Three thresholds deserve direct attention before signing.

First, the one-year holding line is worth real money and is sometimes movable. If shares cross from STCG to LTCG within weeks, waiting can lift net yield from the high-40s to the low-60s in California, or from 57% to 74% in a no-tax state. The trade-off is liquidity risk and the chance the buyer or company-run window closes — a known opportunity cost, not a free option. Second, residency is a planning variable but not a loophole; California scrutinizes departures aggressively, and a sale closed shortly after a paper move invites audit. The sourcing rule favors a genuine nonresident, but “genuine” is a facts-and-circumstances test the FTB litigates hard. Third, the NIIT and California’s lack of a preferential rate mean the marginal cost of an additional dollar of gain is fixed and high — there is no bracket management to be done at this size, only timing and situs.

The structural alternative worth pricing against an outright sale is keeping equity in play through a future transaction rather than cashing out now. A rollover equity tax deferral structure in an eventual acquisition can defer the gain entirely if structured as a tax-free exchange, preserving basis instead of triggering 37.1% today — a different risk profile, but one that keeps the full pre-tax amount compounding. For households comparing a secondary sale against waiting for an IPO, the IPO tax cost for RSU and option holders and the employee net proceeds in an acquisition round out the menu of liquidity paths, each with its own yield profile. The decision is rarely whether to take liquidity — it is which event type, in which state, after which holding-period clock has run. Running the net yield for each before committing is the analytical step that separates a $1,218,000 outcome from a $954,000 one on the same $2,000,000.