sorry for your loss
when did he die? and when was he born (exact dates please).
if he was older than 70.5 in 2019, then yes, he was required to take RMD. if he died in 2020, the rules changed and it may have a different impact.
yes, his 2019 tax return must be prepared and sent it; his passing doesn't change anything
here is what I would do, and it's like being a forensic accountant. Find his 2018 tax return and hopefully the supporting documents (IRA, 401k, etc) are with the return. Contact each company and ask for the 2019 documents so that you can prepare his 2019 tax return.
If you determine he did not take any required RMD's in 2019, get with that company and take it asap. Then you can ask for a waiver from the IRS for the 50% penalty and the reason for the waiver is your father's ill health / passing in 2019. The 2020 RMD is based on the age of the beneficiary and it is still eligible for the 'stretch' provision. If you dad died in 2020, the rules changed. who was listed as the beneficiary on the 401k / IRA - spouse, children, others, estate? the RMD going forward is dependent on that response.
I've made a lot of assumptions here, so let me know if this gets you going in the right direction,.
He passed in Novrmber 2019 at 93 years old. I did receive 1099's for his income(pension and social security) but nothing for his investments which consisted of an IRA, small life insurance and annuity. He definitely did not take his RMD before passing. All of the above investments have been distributed to his beneficiaries(children) at this point.
Also, beneficiaries did take distributions in 2019 which exceed his RMD and are paying taxes on those if that makes any difference,
best to call the IRA trustee and get a copy of his 1099Rs. Call the other companies you mentioned where documents are missing. There may not be one if there were no distributions against his social security # in 2019, other than something that reflects the transfer to the beneficiaries, which has no tax impact for the return
Good to hear the beneficiaries took the 2019 RMD before December 31 - that satisfies the 2019 requirement even though it was the beneficiaries and not your father who actually took the money out of the IRA. The rules is that the RMD, which is based on the December 31, 2018 balance must be distributed by either the owner (your father) or his beneficiaries no later than December 31, 2019. Sounds like that occurred. Nothing to report on your dad's 2019 tax return as it sounds like the IRA was distributed to the beneficiaries and they took the RMD and are responsible for the associates taxes.