Your employer has to report the 10K as an income. Taxes are paid, so if RSU at day of sale be same of day of vesting, you will not need to pay anything (As your employer already paid for it) However if there is a difference in stock price at day of sale you are liable to pay tax on the gain you made, only to the portion you sold.
No way to avoid paying this tax (If you now one let me know :)) The other issue that is a side effect is that the RSU raise your initial W2 income and you may pay more taxes because you are now on higher tax bracket.
