Every year I withdraw money from my IRA. I usually do this at year-end. I then send in an estimated payment for the related taxes. Your system assumes I received the RMD monies all year long and wants to issue a penalty.
I should be able to input my RMD amount in quarterly buckets as well as the tax estimated payments.
Correct...that is the default first calculation that TTX and the IRS uses. This initial/default calculation eliminates the extra paperwork for 60% (a guess) of all underpayment penalty situations.
BUT
It did not for you, so after you have absolutely everything else entered you would go to the Other Tax Situations page in the Federal section...and start thru the Underpayment Penalties section to begin the preparation of the Annualized income method to prepare the form 2210AI with all your quarterly information (not just the RMD...everything).
One way to avoid this, if you are willing, is to make your full estimated tax payment in Q1 every year instead. Then the default calculation indicates you overpaid for at least the first 3 quarters, and might eliminate the need to prepare the 2210AI altogether. Of course, mutual fund distributions commonly occur at year end, and that can waylay the best of plans....overpaying in Q1 to account for those is also possible, but depends on having a financial base of $$ being available. Can also pre-pay 4 smaller-but-equal quarterly amounts (each quarter) to account for the taxes on the expected RMD you plan to take.