How do I correct an entry in schedule c form 8829 before I file?

[AmeliesUncle]

Even if you used the Simplified Method, for this purpose you still need to enter the cumulative amount you could have taken (or just leave it blank and the program will assume that amount).

[lmcolton]

Thank you for trying to help, and I hear what you are saying, but I followed the directions on the IRS 8829 Instructions page (scroll down to Line 31 instructions and also see Part III instructions -- I am unable to post the link here for some reason). On my 2019 tax form that was prepared by my CPA, there was nothing entered at all on lines 32 and 33, so the value that resulted on line 44 was "0" for the depreciation that year. Following the same instructions this year for 2020 I added that "0" to the depreciation I took last year (2020) and got the value 1,947. That is also the value that results from multiplying the percentage they provided in the table on that IRS page (2.5641%), which appears on Line 41 by the Business Basis of the Building on Line 40 (75,914) on my 8829 form for 2020. 

Line 31

Enter any amount from your 2020 Form 8829, line 44.

If you did not file a 2020 Form 8829, then your carryover of prior year excess casualty losses and depreciation is the amount of excess casualty losses and depreciation shown in Part IV of the last Form 8829, if any, that you filed to claim a deduction for business use of the home.

So, following the IRS instructions above, my "excess casualty losses and depreciation shown in Part IV of the last Form 8829" was "0" on Line 44 -- for 2020 and for 2019. 

Line 42

If no additions and improvements were placed in service after you began using your home for business, multiply line 40 by the percentage on line 41. Enter the result on lines 42 and 30.

The IRS instructions above for Line 42 are the crux of the issue, I think. The number that the Turbo Tax system comes up with when it multiplies 75491 x 2.5641% = 1,975. But if you do that math, it is actually 1,947. This must be a calculation error in the system.

[AmeliesUncle]

As I said before, TurboTax uses the Mathematical method of depreciation, rather than using the 'tables' (and whether or not that is allowable for Form 8829 is questionable).

If you leave the "prior depreciation" blank, I think that will fix your problem.

[lmcolton]

Well, I had left "prior depreciation" blank initially, and then I got no 8829 form at all (only the worksheet), and therefore, no deduction. I went back through the process with a TurboTax advisor, and that's when we caught this empty box, so they had me add the depreciation from last year, which was 1947, as I mentioned. Only then, did the system generate the 8829 form with accompanying deduction for this year. So, leaving the "prior depreciation" box blank did not help me, I'm afraid.

I am not sure what "tables" you were referring to. I did not use any myself. The percentage I mentioned, 2.5641%, was automatically generated by the online TurboTax system and automatically appeared on the 8829 the system generated. Looking at the IRS website, however, that percentage does appear in a very simple chart on the page I referred to in one of my last posts under their discussion of Line 42. However, I did not enter the percentage myself; the online system did.