The correct spelling of the contraction is should've.
The contraction is spelled shouldn't.
Both "it is" and "it has" use the same contraction, it's(with an apostrophe).If the context does not make the tense clear, it should be written out.
won't
aren't
The contraction is spelled "doesn't." The past tense is didn't.
The contraction form of who is is who's.Example: Who's at the door?
haven't
you're
I've
They're
contact
QTR.