From https://igotmyrefund.com/4464c-cp05-leaving-taxpayers-confused/
Why am I getting the 4464C letter from the IRS?
Simply put, your tax return is under review. This is not an audit notice. The review is part of a normal revenue protection program by the IRS. The IRS selects returns for review using various methods which include random sampling, computerized screening, and comparison of information received by the IRS such as Forms W-2 and 1099. The letter will indicate that they are reviewing your return for one or more of the following:
At the IRS, it is known as the Questionable Refund 3rd Party Notification Letter. It is sent from the Integrity & Verification Operations unit at the IRS. It signals to the taxpayer that the IRS may contact other parties such as your employer to verify information you reported on your return.
What should I do?
Nothing. It’s not time to call (unless you didn’t file a tax return.) If you receive a 4464C Letter from the IRS, you aren’t required to do anything. The letter indicates that if you haven’t received your refund or been contacted by the IRS in writing within 60 days from the date of the letter you can call for more information. The letter also tells you what to do if you received it and didn’t file a tax return.
so I filed 1/28/2020 i got a 4464c letter Feb 13th advising me to wait 60 days. As of 4/8/2020 it has been 60 days. I have not been contacted from irs and i have tried to contact them to see what is going on but due to covid i cannot reach a live agent. What should I do?
Same here. Got my letter March 11. Can’t get ahold of anyone. I emailed my Congress man, had to fill out privacy release and they would try to get an answer for me. We shall see. Beyond frustrated with the IRS AND TAS. I don’t understand how holding a refund for this long is legal.
As with the President, if the IRS does it, it's not illegal.