There's no way to know. Some number of returns are routinely reviewed and with the COVID-19 shutdown, there is no one to complete the reviews. He only needs to worry if he gets a letter. On the other hand, if his refund is delayed more than 45 days from the latter of the date the return is filed or April 15, the IRS will pay interest on the refund at 5% annually.
On April 2, I filed my tax return electronically from an online tax filing site. I neither owed money nor was due a refund. I started checking the "get my payment" IRS portal daily, especially since I wanted to put my bank account info into the system to get a direct deposit. The media and IRS had claimed this was possible.
For a few weeks at the IRS portal, I would enter my personal info and then get a window saying the IRS "cannot determine your eligibility for a payment at this time." Eventually this changed so that I could enter my AGI from my 2019 return, how much I owed or was owed and a bit more. I did not owe money nor was I owed money. I would put $0 into one of the fields for money owed. No joy: The software was not set up to deal with no money owed nor a refund being due. The online software would not let me enter my bank account info. I kept trying once a day. One day in April the site concluded the session by asking me if I wanted to take a survey. Damn straight. On the survey I flunked the site and growled that the software was not set up to allow those who did not owe, nor were owed, money to enter bank account info. The next day the software evidently changed. For the first time, it let me put in $0 and I was able to enter my bank account information. A few days later when checking the IRS portal the site gave me the day my direct deposit would happen (May 6). The stimulus direct deposit actually showed up a day early on May 5 (today).
I'd say keep checking the IRS portal. Wait a few more weeks before getting concerned.
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