Rmd not taken for 2018

[RWG1950]

Retired wife had inherited an IRA from her mother in 1999 and had been taking RMD's yearly since then.
Wife died in March of 2018 (before taking her RMD) with spouse as her designated beneficiary.
Spouse had neglected to take the 2018 RMD from this IRA.
He has acted to correct this situation & will take both 2018 and 2019 distributions this month.
To be pro-active on this W / IRS & request wavier of the penalty due to the circumstances, what procedure is best to use ?
Thanks for comments.

[Uncle Sam]

Complete P. 2 of Form 5329, at bottom there's a section for you to explain exactly what you did above, that it was an oversight of the beneficiary for a deceased taxpayer otherwise required to take the RMD, show what the RMD should have been, disclosed that it was taken in 2019 prior to the 2018 tax filing and request the 50% penalty waiver.

[RWG1950]

If IRS agrees to waive the penalty, do they send some kind of acknowledgement by letter to the taxpayer ?
Guess something should also be sent to the state (WI). Use the IRS letter ?

[Uncle Sam]

I've never had IRS communicate further once I've submitted the waiver request with a viable explanation.
I can't answer regarding a Wisconsin return.