91 yr old Taxpayer has timely filed Form 4868 with a payment of $10,000.
A preliminary review shows that this taxpayer is seven thousand dollars short due to not including some significant LTCG in 2021. To avoid additional 5% penalties of probably $350/mo he is advised to send an additional 2021 tax payment by May 15,2022. The IRS payment site I found only provides for making 2022 payments.
Would a late additional Jan. 2022 estimated tax payment for 2021 work?
Another 4868 with additional payment???