What does it mean when the Where’s my refund displays a Action Required and says you may have to verify identification

This article should help: Tips for Handling Identity Verification Requests From the IRS 

What happens if I havent received a letter from the IRS? and if so, how long does it take for them to mail out a letter ?

We at TurboTax don't know how long it takes the IRS to send you an Identity Verification Letter.   They may end up verifying your identity without assistance from you, and you won't receive a letter at all.  You'll then see your status go to 'In Process' at the Where's My Refund? link. 

You may want to contact your local IRS Office if more than 60 days goes by without a letter, or a status change.

Here's more info on Identity and Tax Return Verification. 

@Claude Loz

Hello,

I ran into the same issue today. It asked me to verify my information but no letter at all. I did verify my information through ID.me system the IRS uses so would that be more than enough for them? Assuming I never get a letter by mail. I also want to add that when I went back into the IRS page it asked me for a control number but again, no paper notices nor notices through their page.

Thank you!

Here is an FAQ about handling identity verification requests from the IRS.