does name of tax authority and high court also need yo be qupted in case law?

Yes you can quote only case law name.

So we can simply write - for example - in the decided case of Kamal Wahal .. ? We do not need to make reference to the Delhi HC or CIT who were the concerned tax authorities involved in it or the citation number? I am asking because it's tough enough to remember the name of the person without remembering tax authorities and citation numbers.

Yes you can mention that as decided in case of so and so the courts have stated that.....