Did you mean a "2016-47" self-certification letter? The letter is permitted by the IRS to explain a delay past 60 days in rolling money over to another IRA.
Actually this letter - as seen at https://www.irs.gov/pub/irs-drop/rp-16-47.pdf - needs to be sent to the IRA plan administrator so that they will accept your rollover as a rollover. Why? Because otherwise they may treat your rollover amount as a current year contribution, which you do not want.
The IRS does not need a copy of your letter, although you should certainly keep a copy in your tax files in case a question ever comes up. See Section 3, paragraph .01 at the link above.
