I have been selected in MNC as a software Developer. In my initial salary discussion with HR I orally accepted his offer. Now after research I found that offer is not best fitted for me. Can I re negotiate my salary there. I like to mention one thing here till now everything is oral. I need suggestion when I get my offer letter can I re negotiate my salary or I should accept directly that offer?
The oral offer and your oral acceptance doesnt have that much importance (if any, at all). Wait until you get the written offer letter. If you like the offer and the other terms, then accept it. If you don't like the offer, then negotiate. Be prepared, though, to either accept whatever best they can offer or to decline the offer entirely.
In the meantime, keep looking for other jobs, because these "oral offers" sometimes develop this notorious disease of disappearing without any trace.