I'm 18 years old can my parents claim that my passport is missing?

I don't know what country you are from, but in Western countries, you are an adult at 18, and your father (or anyone, for that matter) cannot file a missing passport report, as he is not the holder. You are.

You are an adult. They won't let him make a report of your passport missing - that's your responsibility.

If he reports it stolen, they will want to interview you, and you can show them the 'stolen' passport. And tell them he knew you had it all the time, so he can be prosecuted for wasting police time.

If he does it is likely to be canceled as you are over 18 the police may request you report it, not him....... go to the police yourself and ask them if he can do that as you have your own passport and he is threatening to report it missing, they will take the passport number so if it is falsely reported by him they know it is a false police report and not cancel it

Your father cannot legally hold your passport. If he does not turn your passport over to you, you can file criminal charges against him for identity theft, identity fraud. Tell him to hand over your passport. What he's doing is illegal.

If he files a false police report that your passport is missing, lost, stolen, and you have your passport, he can go to jail for filing a false report.

Tell him to hand over all your documentation (passport, birth certificate, Social Security card, or anything else he has of yours) immediately or he's going to jail. Nobody can hold another person's identification, except parents of a MINOR child (under age 18). As of your 18th birthday, it became illegal for him to possess or use your documentation.

It's not his passport; you're an adult. The police aren't going to take it seriously.

Move out.

You are 18 an adult its your passport
the police cannot return it to him ...

but if you are living in their house ..its their rules

So go to a police station now and ask them to look at your passport and confirm you have it

I don't know yiu have to ask some specialists