Checking a statement: …, phải không?

Say what you think is true, then add phải không? at the end. It works like "…, right?" or "…, isn't it?" in English: Anh là người Úc, phải không? You're Australian, aren't you? In speech there's a small pause before it, which the comma shows.

The answer is about whether your guess was right. Yes is phải, or đúng rồi (that's right), which is just as common. No is không phải, usually followed by the right fact: Không phải, anh là người Anh. Don't answer có: that belongs to có … không.

Phải không fits after any statement, including one with là and a noun, where plain có … không can't go (there you'd say Anh có phải là người Úc không?). That makes it the easy way to check a job, a name or where someone is from: Chị là giáo viên, phải không? You'll also hear đúng không? with the same meaning.

Use it when you already have a guess. If you have no idea, ask with có … không: Mai anh có đi làm không? is an open question, while Mai anh đi làm, phải không? says you think he is. Hả and à also check, but they react to something you've only just heard, and they sound more casual.

Before a verb, phải means "must" or "have to", not a check: Em phải đi làm. I have to go to work.