caution When you receive your shares, you are taxed on their value at that time.* If you are an employee, this means you may have to write a check to the company to cover your income and employment tax withholding. Often, for U.S. employees, companies will withhold the tax in the form of shares such that no action is required by the employee at vesting time.*
If you receive an RSU when the stock is of little value, you cannot elect to be taxed on the value of that stock when you receive the RSU—you pay taxes at vesting time, based on the value of the shares at that time.