We use "have you" when the question is about all of your life. We use "did you" when a specific moment of time (in this case, "yesterday") is mentioned.

Hi there In your first question, 'have you phoned Tom?', you use the present perfect. The present perfect has the fixed form 'has/have + past participle. You use it here because you're talking about an action that happened at an unspecified time in the past. Another example of the present perfect: I have been to China. Again, the action of going to China happened at an unspecified time in the past (we have no idea when), so we choose to use the present perfect. Your second question, 'Did you phone him yesterday?', is formed in the past simple (it's a question, so we use the verb 'to do' in the past simple + verb). Here, you use the past simple because the action is completed in the past. We know that because of the word 'yesterday': you completed the call yesterday (specified time) so we know the action is completely over. Kind regards Karen

They also use "have" when the result of action means something in the actual moment. So like "have you phoned Tom" means also that you should call (or should have called), or you shouldn't, but you did! One more example. Mom asking her kid: have you done your homework? (includes the eyebrow work adding that he better did)

When you say 'have you phoned Tom', you are talking about the situation of this moment, and when say' did you phone Tom', the situation of a past time. ----- Have you phoned Tom? ----- Yes, I phoned him last week/ a moment ago. ------> Then he'll know the day of your wedding and be present.// Then he'll have been crying because he loves you so much and you told him that you had decided to break up with him. // Then you'll not be blamed by your mother because she had asked you to do that. ----- Have you phoned Tom? ----- Not yet. -----> Then he won't be present at your wedding because he does not have enough time to get here before the day. // Then you can think it again if you really want to break up with him. // Then you'll be blamed by your mother because she had asked you to do that yesterday. ------ Did you go to the school sports meet last year? ------ Yes. -------> Then you may have seen John running the 100m that day. /----- Not. --------> Then you would not have seen John running the 100m that day. That said, sometimes both the simple past and the present perfect are possible: ------- Did you phone Tom? [ North American ] ------- Have you phoned Tome? [ British ] If the action or occurence has (or not yet) finished or ended recently, it's observed that the simple past is usually used in North america and the present perfect in Britain. However, the simple past is not used (and the present perfect is) in North America if the action or event continues up to now ( or maybe will last further). For example, I have learned English for three years. ( ✘ Did you learn English? )