Hi Thanks for reply. But the CoS letter with the new employer states that my start date as 09th April 2018.
So can i join them early, that is my question.

Hi, I have just switched to a new sponsor on Tier 2 visa in the UK. The actual start date on the CoS is 09th April 2018. My new visa has been issued on 12th Feb 2018. Therefore, i have got around 8 weeks to join my new role whereas my current employer requires only 4 week notice. Will i be able to ...