The S corporation stock basis you can’t afford to get wrong

Imagine your client, a shareholder, sells every share of their S corporation, celebrates at the closing dinner, then opens a tax notice months later that wipes out half the good news. The culprit almost every time is stock basis nobody tracked correctly.

Selling all the stock in an S corporation may look simple on paper. It isn't. Three parties walk away from the closing table with three very different tax stories, and the seller's story hinges on one number: adjusted stock basis.

Why stock basis is the real deal-breaker

A shareholder's basis generally starts with what they paid for the shares or the carryover basis of property they contributed to the corporation, adjusted for liabilities assumed and other applicable rules. From there, it moves every year. Basis goes up for the shareholder's share of income, including tax-exempt income. It goes down for distributions, losses, deductions and certain nondeductible expenses. It can never drop below zero. The order matters, too. For tax years beginning on or after Aug. 18, 1998, the sequence runs like this: add income first, subtract distributions, subtract nondeductible expenses, then subtract losses and deductions.

When a shareholder sells midyear, adjustments tied to that stock generally apply immediately before closing, not at year-end. Miss that timing and the gain calculation is wrong before it starts. Here's the part clients rarely expect: a shareholder can't deduct losses beyond their combined stock and debt basis. Disallowed losses carry forward, but if the shareholder transfers all the stock, basis-limited suspended losses are generally permanently disallowed. And that is a true story.

What the seller actually reports

Gain or loss is simple in theory: proceeds minus adjusted basis. The hard part is getting to that basis number. Sellers need a paper trail covering the original purchase price, every year of allocated income and loss, distributions taken, nondeductible expenses and any shareholder loans and suspended losses.

A Schedule K-1 (Form 1120-S), Shareholder’s Share of Income, Deductions, Credits, etc., alone won't get you there. It reports allocated items and distributions, but it never states the taxable portion of a distribution or the shareholder's final basis. A shareholder who disposes of S corporation stock generally must file Form 7203, S Corporation Shareholder Stock and Debt Basis Limitations. As the tax professional, that calculation is on you.

What happens to the S corporation itself?

Clients often misunderstand that a stock sale doesn't put a dime into the corporation. The buyer pays the shareholders directly and walks away with the shares.

If the buyer qualifies as an eligible shareholder, the S election generally continues. If not, the election terminates, and the corporation typically has a short S corporation tax year ending right before that termination. The corporation needs to allocate income, deductions and distributions to the seller, generally on a per-share, per-day basis unless an election closes the books, and issue an accurate final Schedule K-1 to that shareholder.

What the buyer should know before signing

Without a special election, buyers generally take a cost basis in the stock. The corporation's assets don't get a matching step-up, which can mean smaller depreciation and amortization deductions than an asset purchase would deliver.

That's where elections earn their keep. A corporate buyer acquiring at least 80% of the target's voting power and value within the 12-month acquisition period may make a joint §338(h)(10) election with the S corporation shareholders, treating the deal as an asset sale followed by a liquidation, generally with a stepped-up asset basis for the buyer. Noncorporate buyers, such as partnerships, can't use that election, but a §336(e) election may offer similar results if the requirements line up.

Why this deserves your full attention

A clean stock basis schedule isn't paperwork. It's the difference between a client who trusts your firm with the next deal and one who doesn't. Sellers need this number handled with precision, while buyers and the corporation have their own basis and reporting considerations. The purchase agreement should spell out elections, final-year allocations and who's responsible for what tax return.

Getting comfortable with transactions like this is exactly what separates a good preparer from the professional clients call first. If you want the education, research tools and community that keep you ready for conversations like this one, that's what NATP membership is built for.