After the following phrases we use the infinitive WITHOUT TO in English:
1. After Auxiliaries / Modals:
CAN
COULD
MUST
MUSTN'T
MAY
MIGHT
NEED
SHOULD
WILL
WOULD
We must go to Rome in September.
They could come with us.
2. After the auxiliary DO:
I don't think so.
3. After the following expressions:
HAD BETTER
You’d better finish your dinner.
WOULD RATHER
I would rather do it now if you don't mind.
WOULD SOONER
I would sooner run the marathon that watch this play.
WHY NOT
Why not ask your mother first?
WHY SHOULD WE?
Why should we go to the cinema tonight?
4. After verbs of perception + object (action has finished):
FEEL
HEAR
NOTICE
SEE
WATCH
…
They felt the rain fall on their faces.
I heard John come home.
5. After LET + object:
Let me go to the fun fair, please.
Let’s have a quick drink.
6. After MAKE + object:
They made her study hard.