To go Fi-Core, you must submit a written request simply stating your wish to "enable your Financial Core status" or words to that effect, to SAG-AFTRA, Attn: Legal Dept. 5757 Wilshire Blvd, Los Angeles, CA 90036.
There are pro-Fi-Core websites that offer sample paragraphs that give a more formal statement of how one might word their letter to request Fi-Core, but the only essential element is “I request to enable my Financial Core Rights” along with your name and performer number.
IMPORTANT: SEND THIS REQUEST BY CERTIFIED MAIL, RETURN RECEIPT REQUESTED AND INCLUDE YOUR ORIGINAL SIGNATURE (not a stamp signature).
This is important because the Union does not have to acknowledge that they received your request in the mail if they do not have to sign for it. Remember, they may call you and attempt to change your mind. If you are resolute, and do not change your mind after enduring their full-court-press to keep you as a member in good standing, you will receive a letter confirming your new status.