Introduction

The present perfect tense refers to an action or state that either occurred at an indefinite time in the past (e.g., we have talked before) or began in the past and continued to the present time (e.g., he has grown impatient over the last hour). The exact time is not important.
We use the present perfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc.
NOTE: You CANNOT use the present perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. In this case, we use Simple Past

Forming

The present perfect of any verb is composed of two elements : the appropriate form of the auxiliary verb to have (present tense), plus the past participle of the main verb.
The past participle of a regular verb is base+ed

And the irregular verbs

For irregular verbs, see the Table of irregular verbs in the section called 'Verbs'.

Affirmative

Subject + have/has + V(past participle)

Subject + have/has + not + V(past participle)

Interrogative

Have/Has + Subject + V(past participle)

Have/Has + not + Subject + V(past participle)

Function

The Present Perfect is used to indicate a link between the present and the past. The time of the action is before now but not specified, and we are often more interested in the result than in the action itself.

BE CAREFUL! There may be a verb tense in your language with a similar form, but the meaning is probably NOT the same.
 

The Present Perfect is used to describe:

1. An action or situation that started in the past and continues in the present. Example: I have lived in Bristol since 1984 (= and I still do.)
2. An action performed during a period that has not yet finished. Example: She has been to the cinema twice this week (= and the week isn't over yet.)
3. A repeated action in an unspecified period between the past and now. Example: We have visited Portugal several times.
4. An action that was completed in the very recent past, (expressed by 'just'). Example: I have just finished my work.
5. An action when the time is not important. Example: He has read 'War and Peace'. (the result of his reading is important)
6. Your experience.

Note: When we want to give or ask details about when, where, who, we use the simple past. Example: He read  'War and Peace' last week.

 

Examples

1. Actions started in the past and continuing in the present. Usually we use it to say 'how long' and we need 'since' or 'for'.

We use 'since' with a fixed time in the past. The fixed time can be another action, which is in the past simple

We use 'for' with a period of time

2. When the time period referred to has not finished.

3. Actions repeated in an unspecified period between the past and now.

4. Actions completed in the very recent past (+just).

5. When the precise time of the action is not important or not known.

6. To describle life experience. These are actions or events that happened sometime during a person's life. We don't say when the experience happened, and the person needs to be alive now. We often use the words 'ever' and 'never' here.