Your Computershare cost basis is the dollar figure that decides how much capital gains tax you owe when you sell, and if it’s blank, zero, or simply wrong, you’ll overpay — sometimes by thousands. You can check it inside your Computershare account, correct it on your tax return using Form 8949, and submit documentation to Computershare so future sales report correctly.
Basis is the number subtracted from your sale proceeds to calculate the taxable gain. Sell for $50 with a $30 basis, you’re taxed on $20. Sell for $50 with a $0 basis, you’re taxed on the full $50. When Computershare processes a sale, it reports the proceeds and (where required) the basis to both you and the IRS on Form 1099-B,1Internal Revenue Service. About Form 1099-B, Proceeds from Broker and Barter Exchange Transactions and that figure flows onto Schedule D of your return.2Internal Revenue Service. About Schedule D (Form 1040), Capital Gains and Losses Garbage in, overpayment out.
Where to Find Your Basis in Computershare
Log into Investor Center and look under “Investments” or “My Account.” Pull two things: the Form 1099-B for the tax year (available by mid-February), and the detailed cost basis or transaction history report. The 1099-B gives you the summary — sale date, proceeds, and the basis reported for covered shares. The detailed report breaks your holdings into individual lots with each lot’s acquisition date, share count, and per-share cost. Some accounts also show a “Cost Basis Statement” summarizing active holdings in one view.
Compare the aggregate basis on the 1099-B to the lot-level totals. If they don’t match, or the 1099-B basis field is blank or marked “unknown,” you’ve located the problem.
Covered Versus Non-Covered Shares
Whether Computershare is even obligated to track your basis depends on when you acquired the stock. Shares acquired on or after January 1, 2011 are “covered” — Computershare must track the basis and report it to the IRS.3Legal Information Institute. 26 USC 6045 – Definition: Covered Security Shares acquired before that date are “non-covered.” Your 1099-B will show the proceeds but no basis, and the responsibility to establish and report the basis is entirely yours. Most of the worst basis headaches involve pre-2011 holdings.
How Partial Sales Are Processed
Computershare uses First In, First Out as the default for partial sales, so your oldest shares go first.4Computershare. Cost Basis and FATCA Information For long-held positions, those oldest shares often carry the lowest basis and generate the largest taxable gain. You can override FIFO and pick specific lots, but only at the time of sale — you have to request it then.5Computershare. Cost Basis FAQ Specific lot identification is not available for transfers; those always go FIFO.
Why the Basis Is Often Wrong
A blank or zero basis almost never means your shares were free. It means someone — your employer, an estate executor, a prior transfer agent, or a Computershare data migration — failed to pass along the right information. A handful of situations account for most of the errors.
RSUs and ESPPs (The Biggest Trap)
Restricted Stock Units vest on a specific date, and the fair market value on that date is reported as ordinary income on your W-2. That same vested value becomes your cost basis in the shares. If your employer doesn’t transmit the vesting price, the 1099-B may show a basis of zero, making it look like you owe capital gains tax on the entire sale price even though you already paid income tax on the vested amount. That’s double taxation on the exact same dollars.
Employee Stock Purchase Plan shares work similarly. The discount gets reported on your W-2 as compensation, and the 1099-B basis typically won’t include that compensation component.6Internal Revenue Service. 2025 Instructions for Form 8949 You have to increase the reported basis by the W-2 compensation amount, or you’ll be taxed twice on the same income.
Inherited Shares
Inherited stock gets a stepped-up basis equal to the fair market value on the original owner’s date of death.7Office of the Law Revision Counsel. 26 USC 1014 – Basis of Property Acquired From a Decedent Decades of unrealized gains can effectively vanish. But Computershare won’t apply the step-up unless the executor supplies the date-of-death valuation.8Internal Revenue Service. Gifts and Inheritances Without it, the system may still carry the decedent’s original purchase price, and you’d pay tax on gains that were legally wiped out at death.
Gifted Shares
Receive stock as a gift and you generally inherit the donor’s original basis — the carryover basis rule.9Office of the Law Revision Counsel. 26 USC 1015 – Basis of Property Acquired by Gifts and Transfers in Trust If your uncle bought shares at $10 and gave them to you when they were worth $40, your basis is $10. If the donor’s basis was higher than the fair market value on the gift date, a separate rule can lower the basis used to calculate a loss. Computershare has no way to figure any of this out without documentation from the donor.
Dividend Reinvestment Plans
Every reinvested dividend is a separate purchase lot with its own date and price. After ten or twenty years of quarterly reinvestments, you can have hundreds of lots. Computershare is built to track this, but data migrations have been known to flatten the lot-level detail. If that’s happened to your account, reconstruct each purchase from the quarterly statements that showed the dividend amount and shares acquired.
Splits, Spinoffs, and Mergers
A stock split keeps your total basis the same and spreads it across more shares. One hundred shares at $15 ($1,500 total) become 200 shares at $7.50 after a 2-for-1 split.10Internal Revenue Service. Stocks (Options, Splits, Traders) 7 If Computershare’s records missed a split, the per-share basis will be wrong even when the total is right.
Spinoffs split your original basis between the parent and the new company based on their relative values right after separation. Parent companies publish an allocation percentage. Computershare should apply spinoff adjustments automatically for covered shares, but verify them, especially for spinoffs that happened before 2011. Mergers that pay cash alongside stock, or cash in lieu of fractional shares, create partial taxable events and need their own basis allocation.11Internal Revenue Service. Instructions for Form 1099-B (2026)
Wash Sales
Sell at a loss and buy substantially identical stock within 30 days before or after, and the IRS disallows the loss.12Office of the Law Revision Counsel. 26 USC 1091 – Loss From Wash Sales of Stock or Securities The disallowed loss isn’t gone — it gets added to the basis of the replacement shares. If Computershare didn’t make that adjustment, your records are understating your true basis on the replacement lots.
Fixing the Basis on This Year’s Tax Return
Correcting Computershare’s internal records helps future sales. It does nothing for a 1099-B already filed with the IRS. For the current year, you correct the number directly on your return using Form 8949.13Internal Revenue Service. About Form 8949, Sales and Other Dispositions of Capital Assets The basic move: report the transaction as it appears on the 1099-B, then use Column (f) to flag an adjustment and Column (g) to enter the correction. Exact steps depend on whether the basis was reported to the IRS.
If the Basis Was Not Reported to the IRS
Your 1099-B will indicate this (typically Box B or Box E on Form 8949). Enter Code B in Column (f), put the correct basis in Column (e), and enter -0- in Column (g).6Internal Revenue Service. 2025 Instructions for Form 8949 You’re supplying a basis the broker didn’t report.
If the Basis Was Reported but Is Wrong
This is the usual RSU and ESPP scenario. Use Code B in Column (f), enter the basis exactly as the 1099-B shows it in Column (e), then enter your adjustment in Column (g).6Internal Revenue Service. 2025 Instructions for Form 8949 The adjustment is a negative number equal to the compensation income already on your W-2, which reduces the gain. The corrected totals carry onto Schedule D. Skip this step and you pay tax twice on the same income.
Updating Computershare’s Records for Future Sales
To fix the basis inside Computershare’s system, contact them and send documentation that matches the source of the shares:
- Direct purchases: old trade confirmations or brokerage statements with price and date.
- RSUs and ESPPs: grant notices, vesting confirmations, and W-2 forms showing the compensation amount.
- Inherited shares: the date-of-death valuation from the estate.
- Gifted shares: documentation from the donor showing original purchase price and date.
- DRIPs: quarterly reinvestment statements showing each date and price.
Computershare charges $10 per year to retrieve archived account statements if you no longer have copies.14Computershare. Schedule of Fees for Computershare Investment Plan (CIP) For decades of holdings those fees add up, but they’re a small fraction of the tax overpayment on a zero basis.
If the Original Records Are Gone
Historical stock price databases, many of them free online, let you establish what a stock traded for on a given date. If you know roughly when the shares were acquired, the closing price on that date is a reasonable starting point. You still need to account for any splits and reinvested dividends between then and now. The IRS expects a good-faith effort, and a documented reconstruction is far better than accepting a zero basis.
Amending Prior-Year Returns
If you already filed with a wrong basis — the classic case is RSU shares sold last year with a zero basis you never corrected — file an amended return on Form 1040-X. The window is three years from the date you filed the original return, or two years from the date you paid the tax, whichever is later.15Internal Revenue Service. Topic No. 308, Amended Returns If you’ve held employer stock through Computershare for several years and never corrected the basis, it’s worth reviewing each year within that window. A single year’s incorrectly taxed RSU sale can produce a four-figure refund.
Penalty Exposure
Basis errors cut both ways. The IRS imposes a 20% accuracy-related penalty on underpayments caused by substantial understatements of tax, and 40% for gross valuation misstatements.16Office of the Law Revision Counsel. 26 USC 6662 – Imposition of Accuracy-Related Penalty on Underpayments The defense is reasonable cause and good faith: keep organized records of your basis calculations, the sources you relied on, and anything you submitted to Computershare. That record protects you whether the IRS questions a basis you reconstructed or a correction you made on Form 8949.