H1 Transfer to new employer approaching H1b visa expiry date when to file extension


I am currently on H1b work visa. My stamped H1b visa through previous employer expires Sept 2016, I changed employers during 2011 and new I797 issued to me expires on April 2017 (3 years from date of issue)

So when should I file extension of my H1b visa, is it by considering Sep 2016 as expiry date or April 2017 as expiry date.

I may need to travel on business out of US and if I have to travel after Sept 2016 I am afraid I have to go for H1b stamping, do I need to have my H1b extension approved before I travel out of US between Sept 2016 and April 2017 timeframe?

Thank you very much for your help.

H-1 extension needs to be filed 6 months prior to April 2017.

If you travel outside US anytime after Sep 2016, then you need to appear for H-1 stamping using the current petition.