If you miss this important letter, you could get shut out of the Medicare claims system. It's time for revalidation of your Direct Data Entry access if NHIC is your HHH Medicare Administrative Contractor. You'll receive one letter listing all DDE users for validation, NHIC explains in an e-mail message to providers. "This letter will be sent to the Primary Institutional Provider address, as listed in the current Operator Control Files." The signed form required for DDE recertification must be returned within 30 days of the date of the letter. "Users who do not re-certify will have their DDE system access terminated," NHIC warns. "After termination, DDE access will be allowed only by applying for access through the existing process." Letters are due by Sept. 6, NHIC says.