There should be no need to split the Form 1099-R. As an example, let's say that your RMD for 2025 was $1,000, which you took, and you later in 2025 converted $2,000 to Roth. The Form 1099-R would have $3,000 in boxes 1 and 2a, box 2b Taxable amount not determined marked, code 7 in box 7 and the IRA/SEP/SIMPLE box marked. I response to the question you are asking about, enter $1,000. On the next page, indicate that Some of the distribution applied to the December 31, 2025 RMD and enter $1,000 as the amount. Next, select "I converted some or all of it to a Roth IRA," then "No, I converted less than $3,000," and finally enter $2,000 as the Actual amount converted. Assuming no basis in nondeductible traditional IRA contributions, the result would be $3,000 on Form 1040 line 4b. (Oddly, TurboTax now seems to also put the $3,000 on line 4a despite the instructions for Form 1040 saying to leave line 4a blank under these circumstances. However, including it on line 4a has no effect on the rest of your tax return.)
