Hypothetical / conditional permission in the present / future

Could = would be allowed to

This is used to talk about permission when we want to use a hypothetical or conditional meaning.

• He could come late. Nobody would mind (= he would be allowed to come late).
• You could stay at home but then I wouldn’t be able to do all the work.
• If John came early to help, Lucy could arrive whenever she liked.

Hypothetical / conditional permission in the past

We use ‘could + have + past participle’ to talk about permission for things that didn’t happen in the past. This is used for conditional and hypothetical situations.

• Could I have gone home early? (I didn’t go home early but I’m asking if it was allowed.)
• Could we have delayed the meeting? (We didn’t delay the meeting but I want to know if it would have been possible.)

We can use ‘could + have + past participle’ in this way to talk about something that would definitely have been allowed in the past, but that didn’t happen.

• I don’t know why he decided not to come at all. He could have come late.