Do (present tense) and Did (past tense)

Present Tense Negative

do + not + main verb

Singular

I do not ___ = I don't ___
You do not ___ = You don't ___
He does not ___ = He doesn't ___
She does not ___= She doesn't ___
It does not ___ = It doesn't ___

Plural

We do not ___= We don't ___
You do not ___ = You don't ___
They do not ___ = They don't ___

Past Tense Negative

did + not + main verb

Singular

I did not ___ = I didn't ___
You did not ___ = You didn't ___
He did not ___ = He didn't ___
She did not ___ = She didn't ___
It did not ___ = It didn't ___

Plural

We did not ___ = We didn't ___
You did not ___ = You didn't ___
They did not ___ = They didn't ___

The verb "do" is a helping verb. We add it to the simple form of a verb to make questions and negatives in the present tense and the past tense.

Examples:

I don't work on the weekend. (present tense negative).
I didn't work last weekend. (past tense negative)
He doesn't like to go to the store. (present tense negative)
He didn't like to go to the store when he was younger. (past tense negative).
They don't have any money. (present tense negative)
They didn't have any money last week. (past tense negative.)

Note: "Do" is also used as a main verb for activities, such as housework, cleaning, studying, research, business, and shopping.

Examples:

I don't do the dishes every night. I didn't do the dishes last night.
She doesn't do her grocery shopping at Cub. She didn't do her grocery shopping yesterday.
They do not do their homework at the library. They didn't do their homework last night.
Their company doesn't do business in Minnesota. They never did business here.

The past tense form of "do" is "did." Did + not = didn't

Examples:
I didn't go to work yesterday.
She didn't take the bus to work.

Separating the contraction creates emphasis

Examples:

I did not want to do the dishes last night. I do not want to do them now!
He does not have his license! He never did get it!
Please, do not put that hot pan on the counter!

Never put did + ____ing

He did going to work last night. (incorrect)
He went to work last night. ( correct )

Avoid bad American grammar!

She don't go to work on Sunday.(incorrect)
It don't matter to me. (incorrect)
He don't know. (incorrect)