Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

To make negative verb forms, add not
Verbs
Multilingual Writers and ESL Topics

If the verb is the simple present or past tense of be (am, is, are, was, were), add not after the verb to form a negative statement.

Gianna is not a member of the club.

For simple present-tense verbs other than be, use do or does plus not before the base form of the verb. (For the correct forms of do and does, see the subject-verb agreement chart on page 182.)

For simple past-tense verbs other than be, use did plus not before the base form of the verb.

In a verb phrase consisting of one or more helping verbs and a present or past participle (is watching, were living, has played, could have been driven), use the word not after the first helping verb.

NOTE: English uses only one negative in an independent clause to express a negative idea; using more than one is an error known as a double negative (see 26e).