Depends on where you are - I believe that's the case in the US, but for example in Australia when RSUs fully vest the value at vesting is included as income on

Depends on where you are - I believe that's the case in the US, but for example in Australia when RSUs fully vest the value at vesting is included as income on your tax return at the end of that financial year, so you don't actually pay the tax until after you file and are assessed.