Net-Share Settlement vs Sell-to-Cover: Which Withholding Default Costs You Less
Two withholding mechanics deliver the same tax result at 22%, but they treat fractional shares and execution slippage differently.
A senior engineer at a public tech company watched 1,000 RSUs vest at $185. The supplemental withholding math should have produced a clean result: 22% of $185,000 is $40,700, leaving $144,300 of stock or cash depending on how the company settled. The actual delivered position was 781 shares of stock, the employee’s brokerage showed a cash entry of $142.76 for “fractional share proceeds,” and the employer’s withholding record showed $40,700 remitted to the IRS. The number of shares that turned into withholding was 220, not 220.54. The difference ended up as a small cash credit from the broker’s auction of the fractional share.
Multiply this across ten vests per year, across multi-grant stacking, and the difference between net-share settlement and sell-to-cover produces noticeable variance in delivered outcomes. Both mechanics satisfy the same IRS withholding obligation under IRC §3402, but they handle fractional shares, commission costs, and execution slippage in different ways.
Net-share settlement, mechanically
Net-share settlement is the simpler mechanism. On the vest date, the company calculates the gross compensation: 1,000 shares times the vest-date fair market value of $185, or $185,000. The company then withholds shares at a value equal to the required supplemental withholding: $40,700 at 22% federal plus any state supplemental plus Medicare.
At a combined supplemental rate of approximately 34% (22% federal + 10.23% California + 1.45% Medicare + 0.9% additional Medicare above $200K), the company withholds shares valued at $62,900. At $185 per share, that is 340 shares. The employee receives 660 shares in their brokerage account. The withheld 340 shares go back to the company’s treasury, and the company remits the cash equivalent from its general funds to the taxing authorities.
The rounding rule
Net-share withholding rounds up to the next whole share. A calculation that requires 340.27 shares of withholding becomes 341 shares. The over-withheld fraction is reported on the W-2 as additional federal withholding. The employee receives credit on the return for the slightly larger withholding. This is usually minor, a few dollars per vest, but it accumulates.
No fractional shares exist in the employee’s account after net-share settlement. The company either delivers whole shares or withholds whole shares. Any fractional entitlement is handled by paying cash equal to the fractional value, which is reported in the employee’s brokerage as “fractional share proceeds” or similar.
Sell-to-cover, mechanically
Sell-to-cover uses a broker to execute a market sale of shares on the vest date. The company instructs the broker to sell enough shares at the opening market price to cover the withholding, remit the proceeds to the company, and deposit the remaining shares into the employee’s account.
On a 1,000-share vest at $185 with $62,900 of withholding due, the broker sells approximately 340 shares at the best available market price. If the opening price is actually $183, the broker needs to sell 344 shares to cover the $62,900. If the opening price is $187, the broker needs to sell only 336. The exact number of shares sold depends on the execution price.
The delivered share count is therefore 660 minus or plus a few shares depending on execution. The cost basis per delivered share is the vest-date FMV of $185, regardless of what the broker actually sold the cover shares for.
Execution slippage
Sell-to-cover introduces execution slippage. On a day when the stock gaps down 2% at open, the broker must sell more shares to raise the same dollar cover, leaving the employee with fewer shares. On a day when the stock gaps up, the employee keeps more shares. Over many vests, the slippage averages out near zero, but any individual vest can feel arbitrary.
Some brokers execute sell-to-cover over a few minutes rather than at the exact open, introducing intraday volatility into the outcome. This is not a planning error; it is a mechanical artifact.
The accounting comparison
Both methods produce the same economic result in expectation. The differences are cash, timing, and fractional handling.
| Element | Net-share settlement | Sell-to-cover |
|---|---|---|
| Shares withheld | Rounded to next whole share | Exact amount from market sale |
| Execution price for cover | Vest-date FMV (no market risk to employee) | Actual execution price (employee bears slippage) |
| Cash to employee | None beyond fractional adjustment | None beyond fractional adjustment |
| Broker commission | None (internal company transaction) | May or may not be charged to employee |
| Delivered share count | Predictable | Variable |
| Cost basis on delivered shares | Vest-date FMV | Vest-date FMV |
The cost basis is identical. The W-2 reporting is identical. The withholding amount remitted to the IRS is identical. The difference is which side of the transaction absorbs execution risk on the cover shares.
When one dominates the other
Net-share settlement dominates when execution conditions are volatile. If the stock gaps down 5% at open on the vest date, sell-to-cover forces the employee to sell more shares at a worse price. Net-share settlement uses the vest-date closing price or some other fixed reference, and the company takes the execution risk.
Sell-to-cover dominates when the employee wants the broker execution to function as an automatic diversification mechanism. A sell-to-cover transaction that happens to remove 40% of the gross share count provides some market entry into the year’s withholding decision. Employees who plan to sell all vested shares immediately anyway find sell-to-cover convenient because the broker handles part of the sale.
The choice is usually not yours
Most plans do not let the employee choose the mechanic. Google, Microsoft, Amazon, and Meta each have a standard settlement pattern that applies to all employees. The choice between net-share and sell-to-cover is a plan design decision by the company.
A small number of plans allow employee election between net-share and sell-to-cover on a per-vest basis, typically through Fidelity or Morgan Stanley’s online portal. If your plan offers this choice, the decision defaults to ease and consistency: net-share settlement requires no action and produces a predictable outcome.
The tax insufficiency problem both mechanics share
Both net-share settlement and sell-to-cover default to the 22% federal supplemental rate on the first $1 million of RSU income. For senior engineers whose marginal rate is 32%, 35%, or 37%, this under-withholds by 10 to 15 percentage points on every RSU dollar below $1M. The mechanic choice does not fix this; the mechanic simply implements whatever withholding rate is required.
Some plans allow the employee to elect a higher supplemental rate through a form filed with payroll. This is rare but increasingly available at large tech companies. When available, electing 32% or 35% supplemental withholding eliminates the need for quarterly estimated payments and smooths cash flow.
The 37% trigger on the $1M threshold
Supplemental wages above $1 million in a calendar year are required under IRC §3402(g) to be withheld at the top ordinary rate, which is 37% for 2025. An engineer with $1.2M of RSU income sees $1M taxed at 22% and $200K taxed at 37%. For an engineer with a marginal rate of 37%, this produces accurate withholding above the threshold and under-withholding below.
The fractional share artifact
A 1,000-share vest at a net-share settlement with 34% withholding produces 660.00 shares delivered. A 1,247-share vest produces 823.02 shares delivered, but because fractional shares are not delivered, the broker’s fractional-share mechanism pays cash equal to 0.02 times the sale price. This tiny credit appears in the brokerage account as “fractional share proceeds” or similar.
Across many vests, these credits can accumulate to hundreds of dollars per year for large holders. They are reported to the employee on a 1099-B as short-term capital gain or loss, with basis equal to the vest-date FMV and proceeds equal to whatever the broker sold the fraction for.
Reporting on Form 8949
Cover shares sold via sell-to-cover, and fractional shares sold under net-share settlement, are both reported on Form 8949 as short-term capital transactions. The cost basis is the vest-date FMV. The proceeds are the actual sale price. The gain or loss is the small execution difference.
Some brokers report the cover-share sales cleanly. Others report them as “unknown basis” or with basis equal to $0, which would produce a gain equal to the entire proceeds. This is a common 1099-B error that requires manual correction on Form 8949 using adjustment code B. Employees should cross-reference their broker’s supplemental statement to establish the correct basis.
Frequently asked
If net-share and sell-to-cover produce the same tax, why does my broker statement look so different?
Sell-to-cover produces visible share sales on the 1099-B. Net-share settlement produces internal company withholding that does not generate a 1099-B entry for the withheld shares. Only the fractional share sale appears.
Does the broker charge a commission on sell-to-cover?
Most large plan administrators absorb the commission. A few charge a per-trade fee that the company reimburses. Very rarely does the commission come out of the employee’s net shares.
What if the stock drops sharply between vest and the sell-to-cover execution?
The employee ends up with fewer shares than a pure vest-date calculation would produce, because more shares had to be sold to raise the required withholding. The W-2 compensation is still based on the vest-date FMV, so the employee may effectively have a tax basis higher than where the stock trades post-vest.
Can I opt into a higher supplemental withholding rate?
Some plans, particularly at Microsoft and Salesforce, allow this election. Check the plan’s enrollment portal or ask your stock plan administrator.
Are the withheld shares still on my cap table?
No. Under net-share settlement, the withheld shares return to the company’s treasury or are cancelled back into the authorized-but-unissued pool. Under sell-to-cover, the shares are sold to whoever bought them in the market and are outstanding in someone else’s hands.
Before you rely on default withholding, compare the delivered outcome at your true marginal rate in the RSU withholding gap calculator.
Fourteen years working with tech employees whose RSU income pushed them into brackets their payroll systems never saw coming. Reviews VestedGrant's RSU and vesting mechanics content.
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