Dear Friends, Please share me your opinions on my question. I did my PhD in germany and also currently working as a postdoc. Since I always worked in academic institutes , I never paid taxes and always received the stipendium not salary. I almost completed 8 years of stay in Germany. Am I eligible to apply for permanent residence permit or citizenship??

If you had all the way a visa under § 18, you can give a shot for the citizenship application.

If you have received scholarships and never contributed tax and pension, there is NO chance for you to obtain N.E(permanent resident) or citizenship.
Even you are working as Postdoc but you are not recognized (by law) as a "Hochqualifizierte" because of the above excuses.

You have to be able to support yourself without ALG II and fulfill the requierment of previous stay on right visa paragraphs and have a Langfristet AE, not necessarily NE, to apply for citizenship. I think technically it is possible, check http://www.info4alien.de/einbuergerung/gesetze/stag.htm#10 (also knowledge of german language, integtation cource etc.)
If your contract is extended after 8 years for a reasonable period of time, why not?

If you got PhD Stipendium, Ausländer Behörde would issue student visa for you. If you receive Postdoc stipendium, there is not much difference in paper(may be of different category). But with those papers, you are not eligible for both N.E(permanent Residency) and citizenship.
As you said, you have not paid tax (and pension as a results).They only issue N.E in accordance with the law and the law(§9) counts the number of months you pay pension scheme as a precondition (of course, there are some other conditions...).
You came to Germany before 1.1.2005, if you apply for N.E in future, besides the pension condition, you don't have to take integration course but you have to show them that you have enough German knowledge.

Dear all,
Thanks for your expert suggesstions. Still I have few more months to complete my 8th year , I would like to give a try. Thanks again

@neoanderson2009

can u pls update on your situation?

HI Raj,
I just completed the 8th year..Not yet started the application process. Surely will update the news in this forum.