I received the same letter, simple tax refund also. Good luck getting help, answers, or even someone sharing their 4464c experience. All anyone does when you post an obvious question like “has anyone else received one” is copy and paste what the letter is or how long you have to wait from the IRS website-Clearly sh*t you you’ve already read a dozen times before breaking down and asking others… It’s frustrating. Obviously you’re not asking anyone to repeat what you’ve already read. If anything happens with mine I’ll let you know ASAP. Good luck
