Normally you'd know if you have an IP PIN because you requested it online or the IRS sent you a
CP01A Notice.
If you're unsure if you have one or not, you can sign in on the
IRS IP PIN website and click on the
Identity Protection PIN link. This should show you any IP PINs you have. If it asks you to enroll and doesn't show you a 6-digit PIN, that means you don't have one.