Is it permissible for a Muslim taxi-driver to transport a female passenger with no other passengers in the vehicle, and if she sits in the back seat?

Answer

It is not permissible for a Muslim taxi driver to be alone with a female passenger even if she sits in the back seat. Rasulullah (sallallahu alayhi wasallam) said that whenever a man and a woman are alone, shaitaan is the third one present.