Is a guide necessary for Sandakphu Trek?

I am planning a Sandakphu - Phalut trek, and I am very confused to whether a guide is necessary for the trek or not. The last time I went on the same trek which was around 5 years ago I remember quite clearly that a guide was not required. I need some help from recent trekkers who have been on the same trek to clarify about the guide, and whether it is compulsory to have a guide.

 

Apparently it is mandatory to get a guide with you on the trek, whether you are in a group or going on your own.

 

Thanks Dhruv, one more question, how do we get in contact with a guide?