Similar to W-2 forms, I "Think" they are required to put them in the mail by 31 January. Then add time in the Postal system to get to your house.
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IF you have an account login for that source, log in and see if it's in there. I found mine in my account, as a PDF download, even though they hadn't told me it existed yet.....but that will vary wildly depending on who is issuing the 1099-R.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*