How does turbotax come up with a number that is much smaller than line 29, schedule C, when that's exactly the instruction for that line?
Line 8 Part II of Form 8829 only starts with Line 29 of Schedule C if 100% of your business income is attributed to your home office.
If you used your home office less than 100% of the time then Line 8 will be prorated to reflect the amount of business income that can be attributed to your home office. For example, if your total business income on Line 29 is $10,000 and you used your home office 25% of the time, but worked at another location 75% of the time, then only $2500 would be shown on Line 8.
This is done because the expenses of the home office are limited to be no greater than the amount of income attributed to the home office. If your home office expense is greater than that limit, it may be carried forward to a future year if you are using the actual expense method and not the safe harbor calculation.
Line 8 Part II of Form 8829 only starts with Line 29 of Schedule C if 100% of your business income is attributed to your home office.
If you used your home office less than 100% of the time then Line 8 will be prorated to reflect the amount of business income that can be attributed to your home office. For example, if your total business income on Line 29 is $10,000 and you used your home office 25% of the time, but worked at another location 75% of the time, then only $2500 would be shown on Line 8.
This is done because the expenses of the home office are limited to be no greater than the amount of income attributed to the home office. If your home office expense is greater than that limit, it may be carried forward to a future year if you are using the actual expense method and not the safe harbor calculation.