While filing my 2023 taxes I discovered I never received my inherited RMD for 2023 until January 12, 2024.
The RMD was paid out within a week and I filed a 5329 to cover the missed taxes for that year in April 2024. How do I now file for my inherited RMD for 2024 when my 1099-R shows both payments combined? I have already paid the missed tax on the 2023 RMD last year.
Both of the distribution that you received in 2024 are taxable on your 2024 tax return. The late-taken 2023 RMD was not reportable as taxable income on your 2023 tax return and should not be present on Form 1040 line 4b or 5b. If it was included on line 4b or 5b of your 2023 Form 1040, you need to amend your 2023 tax return.
Form 5329 has nothing to do with paying income taxes. It's used to calculate additional (excise) taxes as penalties. Given that you received the 2023 RMD in early 2024, you should have requested a waiver of the excess-accumulation penalty calculated on Form 5329 Part IX. (Note that if the 2023 RMD was an annual RMD required under the 10-year rule, no Form 5329 was needed at all since the IRS waived the penalty for failing to take these distributions in 2023.)
To avoid penalty, for that 1099-R, tell TurboTax that the distributed amount is the calculated required amount.
Otherwise you will be in trouble.
If your 2023 return shows a penalty Schedule 2 Line 8, recommend that you amend your 2023 return to file a new Form 5329 with the waiver requested and a revised Schedule 2 with zero in that box.
note that mailed 1040-x , only new or changed forms are attached.
Do not include your old 1040 nor your revised 1040 because the Form 1040-X reflects any changes there and becomes your new tax return.