First, what does the sentence below mean?
He may not have been far wrong
Second, why do we use have rather than has?
English Language & Usage Stack Exchange is a question and answer site for linguists, etymologists, and serious English language enthusiasts. It only takes a minute to sign up.Sign up to join this community
To answer your second question first, as Mari-Lou A has already explained, "may" (just as "must", "can", "should", etc) is a modal verb and, as such, must be followed by infinitive.
As for your sentence "He may not have been far wrong", "far" is an adverb here.
far (adv.) - to a great extent, much (Merriam-Webster)
- That car is far more expensive than ...
- He is able to function far better than usual.
- He felt far better yesterday.
So, your sentence means that "probably he wasn't so wrong"