@RobertB4444 thanks for reply again, i saw this paragraph
"
It is critical, when early exercising an option that the Section 83(b) election is properly and timely filed. If it is not timely filed, then (i) instead of having income at the time of making the election, there will be compensation income to the holder of an NSO (or AMT income to the holder of an ISO) equal to the difference between the purchase price (i.e., the exercise price paid) and the fair market value of the stock on each vesting date and (ii) the capital gains holding period will begin after the restricted stock vests. Again, any compensation income would be subject to all applicable income and withholding taxes (which the company must ensure can be satisfied)."
Since I did not file 83b, I think I should calculate the spread for AMT tax based on FMV each month when RSU( converted via ISO) vested and my exercise price?
If I use the FMV when early exercise as the basis, then file 83b or not will make no difference ?
