Let Someone Do vs. Let Someone To Do
For permission or causation with let, standard English uses let + person + bare infinitive. Cambridge explicitly contrasts this with the nonstandard pattern let + person + to-infinitive.
Use “let someone do something,” not “let someone to do something,” for the ordinary permission pattern.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| ordinary permission/allowance | let + person + base verb | Use the bare infinitive after “let.” |
| passive paraphrase | be allowed to + verb | Use an alternative construction if a “to” infinitive is needed. |
Quick tests
Meaning / construction test
Are you using active “let” to mean allow someone to act?
If yes: Use “let someone do,” without “to.”
If no: If the construction is different, check its own complement pattern.
Examples
Let her finish the explanation.
Active “let” takes a bare infinitive.
They let us enter early.
No “to” appears before the base verb.
We were allowed to enter early.
A passive paraphrase can use “to.”
Further guidance
Boundary
This is different from allow and permit, which normally take object + to-infinitive in the corresponding permission construction.
Construction
Cambridge states that let is followed by an object and an infinitive without “to.”
Decision
After let + person, use the bare infinitive: “let them leave,” not “let them to leave.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Word patterns: let — English Grammar Today (opens in a new tab)Cambridge Dictionary · Let + object + bare infinitive and explicit warning against let + object + to-infinitive