The Project Management Professional designation is conferred upon successful applicants by the Project Management Institute. Holders of the certification are experienced project managers who have completed the PMP exam. Having the PMP certification shows that a person is both highly experienced and knowledgeable about project management -- assuming, of course, that his certification is valid. Fortunately, the PMI makes it easy to check someone's certification online.
Visit the PMI's online registry located at the PMI website.
Fill in the relevant fields. At a minimum you need to enter the person's last name. You also have the option of entering the person's first name, country and specific credential, which in this case would be the PMP.
The more information you provide, the easier it will be to find the right person in the results.
Scroll through the results. If the person you're looking for appears on the list, then you can be certain that she holds a PMP certification. The results will tell you when the person received the certification and also indicate if it's still active, as PMP holders must complete continuing education requirements to maintain an active status.
Be aware that people can opt out of the online registry. While finding someone listed guarantees that the person is certified, failing to find a person in the registry does not necessarily mean she is not certified. If you're verifying certification for employment you should ask applicants to opt in to the online registry.