The verb "do" is a helping verb. We use it to make the present tense and the past tense negative. (Click here for a video that shows the difference between the helping verb and the main verb. )

Examples in the present tense:

I don't work on the weekend. (present tense negative)

He doesn't like to go to the store. (present tense negative)

They don't have any money. (present tense negative)

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

Examples in the past tense:

I didn't work last night.

She didn't go shopping yesterday.

We didn't see that movie yet. .

Be careful: "Do" is also used as a main verb, but only for particular activities, such as housework, cleaning, studying, research, business, and shopping.

Examples:

I don't do the dishes every night. (do = wash)

She doesn't do her grocery shopping at Cub. (do = go/finish)

They do not do their homework at the library. (do = complete)

Their company doesn't do business in Minnesota.

Examples in the past tense:

I didn't do the dishes last night.

She didn't do her grocery shopping at Cub.

Separating the contraction creates emphasis

Examples:

I do not want to do the dishes!

He does not have his license!

Please, do not put that hot pan on the counter!

Never put do + not + ____ing

He doesn't going to work.( incorrect )

He doesn't go to work. ( correct )

Avoid bad American grammar!

She don't go to work on Sunday.

It don't matter to me.

He don't know.