I would disagree with your premise but it’s not your fault. It’s my fault for not explaining it clearly

TBF, i was being a little unreasonably harsh, but i was trying to make a point off of minimal descriptive language so i don't really have much flexibility there.

I don’t think not knowing something makes you stupid. Humans can’t know everything. We all have strengths and weaknesses. I know about taxes, but I don’t know shit about cooking. He cooks dinner, I deal with the bureaucracy situations.

Personally i think being stupid isn't necessarily a bad thing, it's just a lack of education, but i think what really matters is whether or not you weaponize it, if you don't know anything about that topic, you would be relatively stupid in that space, however if you acknowledge that you know nothing and have no practical knowledge basis, that's fine. It's when you know nothing, know that you know nothing, and still engage with it even though you know you have a limited basis to act upon, that it's a problem.

Also, I’m don’t know if you’ve ever spent time with someone who struggles with ADHD and Neurodivergence but their brains don’t work like others. They can’t force themselves to do things that other people can tough out. They can study all night but if their brain can’t stay on track, they won’t be able to retain it.

believe me, i understand it, i'm very ADHD coded, but that usually means i just never get around to doing the things that i need to do (which is relevant here) i don't normally make up weird tangentially relevant reasoning to cope about why i don't do those things though. Personally i find very directed note taking helps a lot with retaining, and it acts as a cheatsheet for when you do inevitably forget about it later on. Though it still requires researching it in the first place.

When I come along and start telling him how tax brackets work, especially if he didn’t ask me, hes going to be frustrated and he’s not going to get through it easily.

there could be a few reasons for this, ignoring external influences, like being pre-occupied, you're either going to have a problem with explaining it, and you need to alter the explanation so it's easier to comprehend, or you're going to have a problem comprehending it, but tax brackets are pretty conceptually simple from my understanding. It should take like 2 minutes to explain the concept of tax brackets to someone, obviously filling them in on all of the details takes longer, but it's the relevant part here.

If you aren't capable of digesting that level of explanation, i'd be concerned about either your level of intelligence, or your ability to care about things. If you aren't capable of caring about something as important as finance, and relatively simple as tax brackets, i'm not really sure what you'd be capable of even conceptualizing in the first place. In my mind, that's either weaponized incompetence, or you have a significant learning disability/developmental disability, as an adult. Which is something that should probably be addressed, obviously i'm not at liberty to talk about any specific person here, but i would personally be pretty concerned by that. Even as someone who struggles with this kind of stuff.

I don’t know if he just doesn’t want to work OT and has settled on this excuse or if there is some other issue but it doesn’t matter. If he doesn’t want to work OT, that’s okay!

Yeah, again not wanting to work OT is perfectly fine, but if that's the reason i'd be confused as to why he's using an irrelevant topic to excuse that, instead of just being upfront about it, seems weird to me on face value. The other option is that he seriously believes what he's saying, even with you correcting him, which means he doesn't trust you, even though you would be the one filing the taxes, which is also incredibly weird. Even if you try explaining it to him, it doesn't seem to matter, so i'm not really sure what the deal is here, but it's weird. Like you see what i mean here right? This doesn't really check out logically in any significant capacity. Granted, it's possible you've left out relevant details that would impact that, but i'm just basing this off of what i'm reading so there's that for take it with a grain of salt.

Regardless of this specific event, it's probably going to influence future recurring behaviors, so it's something to think about. Generally it's rare that people latch onto a specific mechanism of behavior for one, and only that one thing, it usually applies to other things as well.