A founder calls her accountant the day before signing the corporate formation documents. She's contributing a profitable side business — code she wrote, a customer list, $40,000 of equipment — into a new C corporation in exchange for stock. Her co-founder is putting in cash. A friendly angel is buying a sliver of shares at the same closing. "We're not selling anything," she says, "so there's no tax, right?"
Not necessarily. Without careful structuring, that single closing can trigger ordinary income for one founder, capital gains for another, and a phantom tax bill on a piece of equipment with a mortgage attached. The rule that's supposed to make incorporation painless — Internal Revenue Code Section 351 — is one of the most misunderstood non-recognition provisions in the Code. It looks generous on the surface and unforgiving in the details.
This guide walks through how Section 351 actually works, the 80% control test that gates it, the boot and liability traps that quietly blow the election, and the basis math that determines what you'll owe years later.
What Section 351 Actually Says
Section 351(a) is short and famously deceptive:
No gain or loss shall be recognized if property is transferred to a corporation by one or more persons solely in exchange for stock in such corporation and immediately after the exchange such person or persons are in control of the corporation.
Three requirements live inside that sentence:
- Property must be transferred (not services).
- The transferors must receive stock in exchange.
- The transferors, as a group, must be in control of the corporation immediately after the exchange.
When all three are met, no gain or loss is recognized — even if the property has appreciated significantly. The tax isn't forgiven; it's deferred. The transferor's built-in gain gets baked into the basis of the stock she receives, and the corporation inherits the transferor's basis in the assets. The eventual sale of either side will surface the gain.
The 80% Control Test
"Control" under Section 351 has a precise statutory meaning, borrowed from Section 368(c): the transferor group must own, immediately after the exchange:
- At least 80% of the total combined voting power of all classes of voting stock, and
- At least 80% of the total number of shares of every non-voting class.
The test is mechanical and unforgiving. A 79% group fails. A group that meets the test by aggregating five contributors fails the moment one of them is not actually transferring property. And the test must be satisfied immediately after the exchange — not at incorporation, not after the option pool vests, but at the moment the stock is issued.
A few traps that catch founders:
Pre-arranged dispositions. If a founder transfers property and is contractually obligated to immediately sell half her shares to an outside investor, those shares may be excluded from the control test. The IRS treats the integrated steps as a single transaction. The same risk shows up when a parent corporation drops assets into a subsidiary in anticipation of selling the subsidiary's stock.
Disproportionate contributions for hand-holding. Layering in a small contribution from someone whose real role is to push the group over 80% — the so-called "accommodation transferor" — can be challenged. The regulations require that the small contributor's stock not be "of relatively small value" compared to her existing holding, and case law has rejected sham contributions designed only to meet the control test.
Later issuances that dilute control. If the corporation issues stock to a new investor on the same day as formation, the test gets messy. The safer pattern is a clean closing: the founders capitalize, then a separate (and clearly later) financing round occurs.
What Counts as "Property"
Property is defined broadly. Cash, equipment, real estate, inventory, accounts receivable, patents, copyrights, trademarks, customer lists, software code, and even goodwill can all qualify. So can stock of another corporation.
What doesn't count:
- Services. Stock issued in exchange for services is taxed as ordinary compensation income at fair market value, and the recipient's stock is excluded from the 80% control group. A co-founder who is only contributing "sweat equity" can't be counted toward control, and her stock is fully taxable on receipt (or vesting, with a Section 83(b) election).
- Corporate debt not evidenced by a security. Short-term notes don't qualify as property.
- Accrued interest on transferred debt obligations attributable to the post-transferor's holding period.
The services trap is the single most common reason a "Section 351" deal falls apart. If one founder is contributing code, equipment, and customer relationships while another is contributing only future work, the second founder's stock is ordinary income — and may not count toward the 80% test, potentially pushing the first founder out of non-recognition too.
The fix is usually one of two things: (1) have the services-only founder contribute even a small amount of actual property (cash works), so she becomes a real Section 351 transferor; or (2) accept that her stock is compensation and report it accordingly, while making sure the property contributors still satisfy 80% on their own.
The Boot Problem
Section 351 only protects what comes back as stock. Anything else the transferor receives — cash, debt instruments, other property — is called boot and triggers gain recognition up to the boot amount.
The formula in Section 351(b) is straightforward:
Gain recognized = lesser of (realized gain) or (cash + FMV of other property received).
A few features worth memorizing:
- No loss is ever recognized on a Section 351 exchange, even when boot is involved. If you contribute property worth less than your basis, that loss is deferred — and may be permanently trapped depending on how the property is later disposed of.
- Boot is allocated asset by asset when multiple properties are contributed. You can't pool gains and losses across assets to net out the recognized gain.
- Character follows the underlying asset. Boot received in exchange for ordinary-income assets (inventory, depreciable equipment subject to recapture) produces ordinary income; boot received for capital assets produces capital gain.
A founder who wants $50,000 of liquidity at closing — and takes it as cash from the new corporation in addition to stock — will recognize gain up to $50,000, even if the rest of the deal qualifies for non-recognition. That can be the right answer if her basis is high or she has offsetting losses. It can also be a nasty surprise.
Liabilities: The Section 357 Trap
One of the most common ways a "tax-free" incorporation produces unexpected gain is liability assumption. When the new corporation takes property subject to a mortgage, an equipment loan, or assumed accounts payable, Section 357 governs what happens.
Three rules to keep straight:
Section 357(a) — general rule. Liabilities assumed by the corporation are generally not treated as boot. This is what most founders expect, and it's usually right.
Section 357(b) — tax avoidance exception. If the principal purpose of the liability assumption is to avoid federal income tax, or if the assumption lacks a bona fide business purpose, all of the assumed liability is recharacterized as money received — i.e., boot. This rule is rarely triggered in clean operating-business contributions, but it's a live risk when transferors borrow against an asset shortly before contributing it.
Section 357(c) — liabilities in excess of basis. When the total liabilities assumed exceed the transferor's aggregate adjusted basis in the property transferred, the excess is recognized as gain. The classic example: a real-estate investor contributes a building with an adjusted basis of $200,000 and a mortgage of $350,000. Section 357(c) forces $150,000 of gain into income, even though no cash changed hands.
The 357(c) trap punishes leveraged and heavily depreciated assets. By the time a rental property has been depreciated for fifteen years, its basis can be near zero while its mortgage is still substantial. Dropping that property into a corporation looks free on paper and produces a six-figure tax bill in practice. Founders who want to incorporate a leveraged business often need to pay down debt first, or carve the leveraged asset out of the transaction entirely.
Basis: Where the Deferred Gain Goes
The whole point of Section 351 is that gain isn't forgiven, it's deferred. The mechanism is basis.
Transferor's basis in the stock received (Section 358). Equal to the basis of the property contributed, minus boot and liabilities assumed, plus gain recognized. The shareholder's basis in her stock therefore carries forward her old basis in the assets. When she eventually sells the stock, the deferred gain finally surfaces.
Corporation's basis in the property received (Section 362). Equal to the transferor's basis in the property, plus any gain the transferor recognized. The corporation inherits the founder's tax history.
This double carryover preserves the gain on both sides — once at the shareholder level (in the stock) and once at the corporate level (in the assets). It's also why Section 351 transactions need careful documentation: the basis numbers determine taxable income years from now, and reconstructing them after the fact is painful.
A wrinkle worth flagging: Section 362(e)(2) limits the corporation's carryover basis when the aggregate adjusted basis of contributed property exceeds its aggregate fair market value. Without this rule, taxpayers could double up on built-in losses by transferring depreciated property and selling the resulting stock. The corporation's basis is stepped down to fair market value unless the transferor and corporation jointly elect to step down the shareholder's stock basis instead.
"Busted" Section 351 Transactions
Section 351 is mandatory, not elective. If your transaction satisfies all the requirements, non-recognition applies whether or not you want it to. Some founders actively want gain recognition — to use a current-year capital loss, to step up basis before a planned sale, or to start a fresh holding period for Qualified Small Business Stock under Section 1202.
To recognize gain, you have to deliberately fail one of the requirements. The most common technique is to engineer the deal so the transferor group ends up with less than 80% of the corporation immediately after the exchange. For example, the corporation can issue a meaningful slice of stock to a non-contributing party — often an outside investor — concurrent with the founder's contribution. That single fact pattern makes the entire transaction taxable to the founder, and the corporation takes a stepped-up basis in the property.
This is sometimes called a "busted 351." It can be a useful planning tool, but it has to be papered carefully: the IRS can recharacterize a transaction if the non-contributing party is judged to be an accommodation or if the steps are integrated.
Section 351 and Qualified Small Business Stock
For founders eyeing the Section 1202 gain exclusion, a Section 351 transfer is often the event that creates QSBS. Stock issued by a domestic C corporation in exchange for property (other than stock) can qualify as QSBS if the company meets the gross-assets test at the time of issuance — $50 million for stock issued on or before July 4, 2025, and $75 million for stock issued after that date under the OBBBA changes.
A few interactions to keep in mind:
- Holding period. The five-year QSBS holding period starts on the date the stock is issued in the Section 351 exchange.
- Original issuance. QSBS must be acquired by the founder at original issuance from the corporation. A Section 351 exchange in which the founder contributes property and receives newly issued stock qualifies.
- Asset test at issuance. The corporation's gross assets (including the property just contributed) must be at or below the threshold immediately after the issuance. Contributing $40 million of property the day before crossing $75 million matters.
- Replacement QSBS via later 351 exchanges. If QSBS is later exchanged for stock in a different corporation in a qualifying Section 351 transaction (where the receiving corporation has 80% control of the exchanged corporation), the new stock can be treated as QSBS that tacks the original holding period.
This is why an apparently dry incorporation event can be worth millions of dollars of tax savings five years later. Get the structure wrong at formation and a future QSBS exclusion can vanish.
A Practical Checklist Before You Sign
Before closing a Section 351 transaction, work through these questions:
- Who is in the transferor group? List every contributor, what each one is contributing, and how much stock each receives. Confirm that the group, in aggregate, will own 80%+ of voting power and 80%+ of each non-voting class immediately after closing.
- Is anyone contributing services? If so, that person is not a Section 351 transferor for the property portion. Their stock is ordinary compensation. Make sure the property contributors still satisfy 80% on their own.
- Is there boot? Cash distributions, promissory notes, and other non-stock consideration trigger gain up to the boot amount.
- Are liabilities being assumed? Run the Section 357(c) math: do total liabilities assumed exceed the transferor's aggregate basis? If so, the excess is taxable.
- What is each transferor's basis going in? Document this contemporaneously. You'll need it for Section 358 (stock basis) and Section 362 (corporate basis).
- Is there a planned subsequent transfer? Stock dispositions arranged at the time of the contribution can be integrated into the deal and may bust the control test.
- Is QSBS on the table? Confirm the corporation's gross assets are below the Section 1202 threshold immediately after the issuance, and that the corporation is a domestic C corporation engaged in a qualified trade or business.
- Are you filing the right statements? Both the transferor and the corporation must attach a statement to their tax returns under Treasury Regulation Section 1.351-3 describing the exchange, the property transferred, the stock received, and the basis carryover.
Why the Paperwork Matters
Section 351 is a documentation-heavy provision masquerading as a simple non-recognition rule. The numbers that matter — the basis in each contributed asset, the fair market value at the time of transfer, the allocation of stock among contributors, the identification of any boot or assumed liabilities — must be tracked from day one. Reconstructing them five years later, when the founder sells the company or claims the QSBS exclusion, is significantly harder.
This is where careful financial records pay off. Founders who keep contemporaneous, plain-text records of their incorporation — asset-by-asset basis, liabilities at the time of transfer, the identity of every contributor — have a clean audit trail when it matters. Founders who rely on a single spreadsheet that lives on someone's laptop typically don't.
Keep Your Founder Records Audit-Ready From Day One
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