Not sure how my "prior depreciation" could be wrong. I entered exactly what appeared on my 8829 form last year, which was calculated correctly. This year, when the online prompt asked me what the depreciation was in prior years, I input the exact depreciation from last year (1,947). The percentage has not changed on line 41 and the Business Basis of the Building has not changed from last year. So then, it is simple math. When you multiply the percentage (2.5641%) on line 41 of the 8829 form times the value provided on line 40 of the 8829 form ($75,914), the answer that TurboTax provides on line 42 is 1,975 (wrong); it should be 1,947 just as it was last year. So, it is off by $28. I really think it is a miscalculation.
