Your point is valid - and I'm doing exactly that. This is why I'm stymied. There is absolutely nothing different I've entered for these tests (with the 2023 return) than with prior returns. Since this IRA is totally tax-deferred - I've never had a situation to enter a split for taxation. When I retired I executed an NUA option to break out all NUA eligible stock into a brokerage account, then had accumulated some after tax funds to pay my cost basis tax obligation). All post-tax contributions to my 401K were exhausted before I rolled all the pre-tax funds AND my retirement cash balance into my rollover (pre-tax) IRA.
Yes, the 4A and 4B lines are different. As I stated, they are not fixed - as I test 20K increments - the percentage of taxation creeps up slowly in that low 50% range.
