There are many ways of requesting permission in English. However, knowing when to use the right request formula or structure is a bit tricky. This can be determined by asking yourself these questions:

* Does the other person have higher status than you? (e.g. more authority or older)?
* Is the other person a stranger, an acquaintance, a colleague, a friend or a relative? (You don’t need polite formulas with people you know well – it sounds sarcastic.)

* Is your request going to cause the other person trouble or extra work?
* Is the other person in a good mood or a bad mood?

* …Could I use your phone?
* …Might I possibly use your phone?
* …Sorry to trouble you, but do you mind if I use your phone?
* …Would you mind if I used your phone?
* …May I use your phone?
* …Can I use your phone?
* …I wonder if I could use your phone.