How does RSU factor into annual tax? Does unsold RSU count as income for that year? or only sold RSUs

[borui-wang2013]

For example, my W2 income for the year is 200k, and I have another 200k of unsold vested RSU, so does my total income count as 200k for the year or 400k?

[Critter-3]

200K

When you sell the stock you still own the taxes are paid in that tax year on the profits only.

[TomD8]

RSUs are taxed as income to you when they vest, and their value is included in the compensation reported in Box 1 of your W2.  That income is subject to federal and employment tax (Social Security and Medicare) and any state and local tax. The income is subject to mandatory supplemental wage withholding. 

Thus your taxable income in your scenario would be $400K.

When you sell your vested shares, you will have a capital gain or loss, based on their change in value since the vesting date.

[Rick19744]

Hopefully @TomD8 response was not a surprise. 

I am surprised that the company did not provide an explanation of how this works.  Especially, since you will have significant withholding (as noted by TomD8).  If you haven't already, you need to discuss this with the company so you understand how the withholding taxes will be paid; some companies have more than one option, but in general, most taxpayer's sell some of their RSU's back to cover the tax implications.