You received a Letter 4743 in the mail about your PTIN (preparer tax identification number) account as a follow-up security measure to ensure you are aware that a PTIN account was created for you. This letter is intended to confirm that you are informed about the creation of the PTIN account. If you believe that someone inappropriately created an account on your behalf, you should contact the IRS Tax Professional PTIN Line to report it. Otherwise, no action is necessary on your part.
Sources:
Notice 2011-6
Notice 2011-80
Publication 947 (2/2018)
Publication 3452
Notice 2011-11