has, does, doesn’t

In nonstandard and casual speech, the -s verb form has, does, or doesn’t is sometimes replaced with have, do, or don’t. In standard English, use has, does, or doesn’t with a third-person singular subject.

Present-tense forms of do (including negative forms)

Present-tense and past-tense forms of have

When to use the -s (or -es) form of a present-tense verb

Exercises:

Standard English verb forms 1

Standard English verb forms 2

Standard English verb forms 3

Verb tense and mood 1

Verb tense and mood 2

Verb tense and mood 3