Modal verbs for expressing permission

Modal verbs:
asking for, giving, refusing permission
present or future past tense
We use can when we give someone permission to do something:

You can bring a friend to the party if you want.
You can borrow my phone if your battery is dead.
We use could to say that something was permitted in the past:
Many years ago you could smoke in cinemas, but now it's banned.
We also use may for permission.
May is more formal and is used less often than can:

Passengers may take one small bag on board the plane.
We also use was / were allowed in the past:

We had to wear a tie at school, but we were allowed to take it off in hot weather.
Refusing permission

We use can't to say that something isn't permitted:

You can't park here – it's private property.
He can't drive my car – he doesn't have insurance.
Refusing permission

We use couldn't / wasn't allowed to to say that something was not permitted in the past:

We couldn't cross the border without our passports.
Must not / mustn't is also used for permission, but is more formal. It is often used on signs and in announcements:

Passengers must not speak to the driver while the bus is in motion.
Asking for permission:

We use Can I? / Could I? / May I? to ask for permission.
1. Can is informal: Can I speak to John Wilson, please?
2. Could is more formal and polite: Could I speak to John Wilson, please?
3. May is the most formal: May I speak to John Wilson, please?
Asking about the past:

We use was allowed to? Could you? to ask if something was permitted in the past.

Were you allowed to stay up late when you were a child?
Could you stay up late when you were a child?
Could people travel between East and West Berlin during the Cold War?
See also: Modal verbs to express ability >>

See also: Making requests in emails >>