"Meaning, we asked for a significant amount more than the usual 22%, which they did hold back. But this additional amount is not reflected on the W-2."
and
"They were supposed to have withheld 33-35% on the RSUs and it looks, from our W-2, like only 22% was withheld. This is where we're hoping that something additional will show on the 1099-B because the W-2 doesn't seem to include everything."
Well, maybe the payroll department didn't do what you asked, maybe they did and you're just not seeing it, but talking it over with the payroll department is the only way to determine what they did.
"In the statements we can see on our brokerage website, the shares held represent a much higher percentage. So why is this not reported on the W-2?"
I think what you're saying here by "shares held" is that the shares that got sold "to pay for taxes" is higher than you'd normally expect it to be and you can't trace that "higher" amount to your W-2?
One answer to the question as to "where are the extra taxes showing up in my W-2?" could be a misunderstanding on your part. Shares sold "for taxes" encompass all the taxes normally associated with a paycheck; federal withholding, state withholding, local taxes, FICA, possibly state unemployment taxes, state disability tax, etc. So those "extra taxes" could and should be showing up in more than just your federal income tax withholding. Again, the payroll department should be able to map this out for you.
"I'm not sure what it means to use the "wrong basis," so I guess we'll have to look into that once we receive the 1099-b."
Here's the problem; ever since (I think) 2010 brokers have been reporting the wrong basis for employer stock on the 1099-B. They are supposed to supply the correct numbers with some sort of additional statement that comes with the 1099-B but it seems like lots of people don't see this statement and only look at what's on the 1099-B. In the case of RSUs they report $0 as the basis since the broker's requirement is to only report what you paid out of pocket for the shares. The actual per-share basis is the same per-share number used by the employer to calculate the compensation created by the vesting of the RSUs.
