Present Perfect Simple

Form

• Active: have / has + past participle. Example: She has visited Paris three times.
• Passive: object + have / has + been + past participle. Example: Their project hasn't been finished yet.
• Negative: haven't / hasn't + past participle. Questions: Have / Has + subject + past participle?

Use

• Completed actions with a present result: The doctors have treated many patients today.
• Life experiences: I have never seen a surgery before.
• How many times / how much: She has visited Paris three times.
• Actions that started in the past and are still connected to the present: Hospitals have improved their emergency systems recently.
• Time words: just, already, yet, ever, never, recently, so far, for, since.

Active to passive

• Someone has stolen my bicycle. -> My bicycle has been stolen.
• They have built a new hospital. -> A new hospital has been built.
• The students haven't written their essays. -> The essays haven't been written yet.
• People have consumed too much sugar. -> Too much sugar has been consumed.

Common mistakes

• "I have studied all night" for a tiring, continuing activity -> I have been studying all night.
• has know -> has known; have be improved -> have been improved.
• "How many times have you been seeing...?" -> have you seen (counting uses the simple form).