The Protected Filing Date (PFD) is the date you contact Social Security and ask to file a disability application.
What is so special about that?
The PFD is used to determine how far back your benefits can be paid.
What makes it “protected?”
Since the application process takes time, Social Security does not want to penalize you for delay between the time you ask to start an application and the time you actually finish it.
For example: if you contact Social Security on March 1st to start an application, but do not turn in all the paperwork until April 1st, Social Security will use March 1 as your protected filing date (even though you did not actually turn in your application until April).
This could mean an extra month of benefits for you.