@jwspring
A breakdown of the sources for lines 25a, b, &c are shown in the "Tax Payments Worksheet" (but even some of these might be combined from other entries....but it's a start) For instance, on one of my test files, the source of line 25c happened to be a form W-2G.
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To find the "Tax Payments Worksheet" , It depends on which Software you are using.
1) For Desktop software, you just open your tax return, and switch to Forms Mode. Then scroll down the list of federal forms to the "Tax Payments" form and open that. All sources of federal withholding will be shown in lines 10 thru 18f.
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2) For the Online, internet browser-based software (2021 only).......you'd need to first get into yoru tax file, then go into the Print Center, and save a copy of yoru tax file to a PDF file, , but make the selection to include all possible worksheets. then the "Tax Payments Worksheet" is one of the sheets in that PDF file.
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3) For the Online, internet browser-based software (2020 tax files and earlier)....You would log into the tax account you used that year (hopefully the same one you used for 2021 taxes)....find your prior year tax file, and download a NEW PDF file from that year, and it's in there.
(All prior year tax files ..2020 and earlier...now contain only the huge-full PDF file with all the worksheets. 2021 files will be saved that way too, but only after sometime in ~Nov of 2022, after the 2021 tax season ends)
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
