If he had walked to work, he would have been late

[Dharminder Singh]

Do we always use have with would? For example in the following sentence.
"If he had walked to work, he would have been late"

My doubt aroused because with "he" we always use "has". Then why are we writing "he would have" Instead of "he would has"?

 

[Piscean]

The form following the modal would is the infinitive form have.

 

[Tarheel]

Try:

Why do we say "he would have" instead of "he would has"?

Because.