对吗 / 对不对 / 好吗 / 是吗【duì ma / duì bu duì / hǎo ma / shì ma】

A tag after a statement turns it into a check. The statement comes first, then a comma, then the tag. The tag you pick depends on what you're checking.

对吗 and 对不对: is that right?

These check a fact you think you know.

好吗 and 好不好: is that OK?

These ask for agreement to a suggestion or a request. 行吗 and 可以吗 do the same.

Mixing the two up is the usual mistake. 好吗 doesn't check facts.

• × 你是英国人，好吗？ → 你是英国人，对吗？

是吗: really?

是吗 on its own reacts to news, like "really?" or "is that so?".

是不是 also works as a tag; it has its own point.

One question marker only

The statement before the tag takes no 吗, and an A-not-A tag takes no 吗 either.

• × 你是老师吗，对吗？ → 你是老师，对吗？
• × 我们走吧，好不好吗？ → 我们走吧，好不好？