Hello All,
I entered Germany in March 2012 on a time limited contract of 3 years (intra company deputation from my home country). I was issued a residence permit only till Nov. 2014 as my passport was valid only till then. Later I got my passport extended and applied for the extenstion till Feb 2015 (i.e. the validity of my employment contract). Till then Blue card had come into existence and I got a Blue card till Feb. 2015. Then my contract got extended by 1 year and accordingly the blue card was also extended. I have my current blue card till May 2016 (end of employment + 3 months). My current employment contract will expire as planned in Feb. 2016.
Now I am about to get a new employment contract from a different employer in the same city with the start date of 01.04.2016 or 01.05.2016 i.e. within the validity of my current blue card. The contract meets the requirements of Blue card.
My questions are as follows -
1) I understand I can't start with the new job as the employer has changed and I need to first get the approval from the authorities. is it correct?
2) Is it a simple case of extension (similar to a change of employer within the validity of Blue card) or a new process with any chances of rejection?
3) Not to take any chances, I would like to go back to my home country and join my job from 01.03.16 there and come to Germany when I get an appointment with foreigner's office for the extension. Is it going to have any impact on the process?

Thanks in advance for your inputs!   

Hello,

1) Yes, you need to inform the Auslanderbehorde.
2) My guess is that they'll issue you a new Blue Card, or maybe just an extension with a different employer name on it. In any case it shouldn't be a problem, if your new job meets the requirements they won't reject your application.
3) You can but you don't have to. As long as you have a valid residence permit you can do everything from Germany.

Additionally, if you have a higher education degree you may also qualify for a permanent residence permit. I can give you details if that's the case.

Best,