I am currently in an MPI position and with no credentials. Can the commander write a memo for me so I can do MPI duties?

As an MP you can investigate, enforce, and uphold all regulations you are allowed to enforce on your base. Mp's can take statements, participate in investigations, (with guidance from CID), and do all kinds of things. You can do just about everything CID can. Just work with them and learn as much as you can until you go to school. Good Luck.

I was an MPI as an A1C and didn't go to school until I was a SrA. You can perform all the duties but will not be credentialed until after MPI School. Unless the regs state you are not allowed to carry out the assigned duties.

Continue to soldier on in your current position as an MPI assistant/helper. Learn everything you can about the actual duties and responsibilities of an Military Police Investigator. Take a lot of notes, that will help you when you go to school in March. Read SGT William's comment again, he is right on with his information and guidance. And Good Luck with your future assignment as an MPI Investigator.