I certainly understand your comments, but I am close to an expert (but obviously not infallible) on paycheck breakdowns. I have a spreadsheet that calculates my paychecks to the penny, and then summarizes everything and calculates the Fed and State taxes, as well as the W-2. It also handles investments like RSUs. I just use TTAX to file - my taxes are already done (except for 1099-R/INT/DIV stuff) before I even download TTAX each year.
This is necessary for me, because without that tax planning tool, I may end up with underpayment penalties. I have to make my Q4 Estimated Payment by mid-January, so waiting for W-2s to arrive in late January is not an option for me. It also helps me make sure I max out my 401k contribution on the last payroll period, which ensures I get the max employer contribution. When the W-2s finally arrive, I just check to make sure everything is correct.
It's complex for sure! Knowing how to calculate federal taxable wages on a paycheck by paycheck basis can be tricky. But I have managed to figure it out and build an Excel XLS that does it all - been doing so since 1998. Each year I just need to update the tax rate tables, standard deductions, etc. I just forgot to update the FICA max in my 2023 version, which caused this issue.
Apologies for wasting everyone's time and appreciate the willingness of everyone to help!
