Tax burden higher when filing jointly than separately. Am I making an error?
I'm currently finalizing 2025 taxes and running into some confusing numbers, wanted to see if this makes sense or if I am doing something wrong.
My wife and I are both high income earners. I have some K-1s that often take until mid-late summer to return, so I file an extension on my tax return. For the sake of claiming some refund due and for getting my wife's student loan IDR plan recertified, we typically file her taxes on time as married filing separately. Then when I get my K-1s, we amend her return to married filing jointly with my income and K-1s. This year we did the same, and she got a federal and state (OR) refund. I paid almost the perfect amount of tax so I didn't owe anything when I filed my extension.
As I am running through the process of amending our returns this year in FreeTaxUSA, the calculations aren't making sense to me. When I compare the federal tax burden for married filing jointly, it is actually higher than the combined tax burden of married filing separately. This seems to come from the deductions. We itemize because we have a high mortgage interest, so we are always above the standard deduction. On the joint return, schedule A line 5e is $10,000, much lower than the amount in line 5a, presumably because our combined income is too high to get a full SALT deduction. On my wife's separate return, line 5e is $20,000, presumably because her individual income is below the ~$250,000 threshold. So basically what happens is her individual itemized deduction is about the same as the joint itemized deduction, slightly above the standard deduction. The combination of our filing separate itemized deductions is therefore larger than our filing jointly deduction, and the refund increases.
Does this make sense, or am I missing something/making a mistake in the data I entered?