S corp basis: how stock basis is built and tracked year to year

“In computing stock basis, the shareholder starts with their initial capital contribution to the S corporation or the initial cost of the stock they purchased (the same as a C corporation).” IRS, S corporation stock and debt basis

Where does S corp stock basis start?

S corp stock basis starts with what the shareholder paid for the shares or contributed to get them, and the starting figure depends on how the shares were acquired. According to the Instructions for Form 7203 (Rev. December 2022), purchased stock usually takes its cost. Stock received for property in a section 351 transaction generally takes the carryover basis of the contributed assets, less any liabilities the corporation assumes, under IRC section 358, with section 357(c) applying when assumed liabilities exceed that basis. Inherited stock generally takes fair market value at the date of death or the alternate valuation date, gifted stock generally keeps the donor's basis, and stock received as compensation takes its fair market value when included in income.

Later contributions and purchases are added on Form 7203 line 2. Shareholder loans never enter stock basis. They create debt basis, which is tracked separately.

Line by line entries for every Form 7203 field are on the Form 7203 page.

How does the Treas. Reg. 1.1367-1(g) election change the order?

The Treas. Reg. 1.1367-1(g) election lets a shareholder subtract losses and deductions from stock basis before nondeductible expenses, swapping the last two steps of the default order in Treas. Reg. 1.1367-1(f). The default order runs income, distributions, nondeductible expenses, then losses. By default, nondeductible expenses above stock and debt basis drop away, while excess losses are suspended and carried forward.

Under the election, losses get the first claim on basis. Any nondeductible expenses still left once stock and debt basis reach zero carry into the next year and are treated as that year's nondeductible expenses. The shareholder elects by attaching a statement to a timely filed original or amended return agreeing to the carryover rule, and the Instructions for Form 7203 add that the statement names the S corporation. The election then applies to every later year for that S corporation unless the IRS consents to a revocation. On Form 7203 it is flagged in item E, and nondeductible amounts move from lines 8a to 8c to line 13.

How is stock basis tracked when shares have different bases?

S corp stock basis is tracked share by share under Treas. Reg. 1.1367-1(b)(2) and (c)(3). Each share takes its part of income, losses, deductions and distributions on a per share, per day basis under IRC section 1377(a). When the decrease allocated to one share is larger than that share's basis, the excess reduces the remaining basis of the shareholder's other shares in proportion to their remaining basis. That matters when one block is later sold, because gain uses the basis of the shares sold. Item C of the Instructions for Form 7203 allows more than one Form 7203 for the periods before and after a partial sale or redemption.

For example, a shareholder holds 500 original shares with $5,000 of basis and 500 shares bought later for $20,000. A $15,000 loss passes through, or $15 per share.

The later block ends at $20 per share. A pooled $10 per share would overstate the original block by $5,000 and understate the later block by the same amount.

What does a multi-year S corp stock basis calculation look like?

A multi-year S corp stock basis calculation carries each year's ending basis into the next year as line 1 of Form 7203. For example, Dana forms a calendar-year S corporation in January 2024 and owns 100% of it. She contributes $40,000 of cash and equipment with a $15,000 adjusted basis, with no liabilities assumed, and makes no loans. Her 2024 K-1 shows $500 of interest, $10,000 of distributions, $1,000 of nondeductible expenses and a $30,000 ordinary loss.

Her 2025 K-1 shows $6,000 of distributions, $3,000 of nondeductible expenses and an $8,000 ordinary loss. The table compares the default order with the Treas. Reg. 1.1367-1(g) election.

With the election, Dana deducts the full $8,000 loss in 2025 and carries $2,500 of nondeductible expenses into 2026, where they reduce basis before that year's losses. Without it, $2,500 of loss waits for future basis. Because the election binds later years, model more than one year before attaching the statement.

What do reviewers check on S corp stock basis?

A reviewer checking S corp stock basis first confirms the documents behind the starting figure, then confirms that each year's adjustments followed the ordering rules in Treas. Reg. 1.1367-1. The starting point is the prior-year Form 7203, because line 1 should match last year's line 15 unless this is the first year of ownership. For a client new to the firm, the reviewer asks for the formation or purchase documents and every earlier Form 7203 or basis worksheet, since a basis error made years ago carries into every later loss and distribution. The reviewer also confirms whether a 1.1367-1(g) election statement was ever attached for this S corporation, because the election stays in effect without being restated each year. Where the shareholder holds blocks with different bases, the reviewer confirms that a partial sale used the basis of the shares sold. The six checks below each tie to the Instructions for Form 7203 or a Treasury regulation.