About 10% of applications for passing the PMP Exam are audited (that is, one out of ten).
Do not panic if your application is audited. Yes, you have to tinker a bit - but it will not be a significant obstacle. Validation is purely formal.
If the application falls under audit, the applicant is sent a letter saying that he will have to confirm experience and project management training in writing. To do this, fill out the attached form letter, signed from superiors or project sponsors where the applicant states his experience, and then send that to PMI. This document, together with the signature and seal of the applicant shall demonstrate that he/she has passed the required training.
The form must be sent by regular mail or courier service (for example DHL).
In an extreme case, the auditor from PMI can call the person who confirmed the experience of the candidate and ask a few questions about the project.