> From my perspective K1s, RSUs, & ESPPs are as simple as a W2 with state tax withholding and I think that is why I am struggling with so many of the comments on this post - I simply can't relate.

Well, you are an accountant :-)

With my K1, the issue was that it was for a real estate investment, and you have to be careful about things like bonus depreciation/cost segregation etc. One tax accountant I used was not carrying over the loss (or perhaps not applying the prior year's loss, or something like that). Another accountant was deducting that loss from my W-2 income, which I can't do as I'm not a real estate professional.

When I finally brought these points up and got all these corrected, I studied the final result and then continued doing them myself. But it was a pain getting the online tax SW (TurboTax, TaxAct, etc) to mimic what they did. I had to be really careful what things I said "Yes" to and what I didn't. I would never have figured it out on my own by reading the relevant tax publications (which I did peruse).

And then later, I formed a partnership with a friend so we could both invest in something. Now I also have to issue K-1s! Not fun! RSUs are much easier.