Necessary or Needful

[sahanav]

Which one is right?
‘I shall do the necessary’ or 'I shall do the needful'
Thanks in advance

[SoothingDave]

This is an innovation of Indian English.

Needful is an adjective. Necessary is most always used as an adjective.

I would say "I will do what is necessary" or "I will do the necessary things."

[sahanav]

Which means it cannot be used with SHALL is it? Only with will.

[bhaisahab]

Which means it cannot be used with SHALL is it? Only with will.

You can use it with "shall", it's just that in the US and the UK we tend not to use "shall" very much any more. It's perfectly acceptable in Indian English, as is "do the needful". "Do the necessary", however, is not used.