Our English is the goodest

From the IRD's page on spotting phishing scams:

Warning signs to watch for

If you receive an email asking for your tax information including your IRD number, password or user ID you should always check:

- is the sender's email address "@ird.govt.nz"?
- does the login page start with "https://"?
- does the website have "govt.nz/" in the address?
- does the text use poor spelling or grammar?

If you answered "No" to any of these question, delete the email permanently and also delete it from your trash

So in other words, if the text does use poor spelling or grammar then it must be from the IRD...