Updated October 18, 2026. Quick answer: Line 27a is the energy efficient commercial buildings deduction and line 27b brings in the total from Part V line 48. Line 28 adds lines 8 through 27b, and line 29 subtracts that total from gross income on line 7. Line 29 is the tentative profit before any home office expense on line 30.
Business use of your home (Form 8829), the saver’s credit (Form 8880), clean vehicle credits (Form 8936) and amended returns (Form 1040-X), read line by line: Form 8829 lines 8 to 15 and Form 8829 lines 16 to 27.
What lines 27a to 29 ask for
The form captions line 27a as “Energy efficient commercial bldgs deduction (attach Form 7205)” and line 27b as “Other expenses (from line 48)”. Line 28 reads “Total expenses before expenses for business use of home. Add lines 8 through 27b”. Line 29 reads “Tentative profit or (loss). Subtract line 28 from line 7”. They finish Part II of the Schedule C (Form 1040).
Line 27a: the energy deduction
The instructions say a taxpayer “may be able to deduct part or all of the expenses of modifying an existing commercial building to make it energy efficient.” They add “For details, see Form 7205 and its instructions. Attach Form 7205 to your tax return.” The instructions also note in their summary of changes that the expense “is now reported on line 27a.” The amount comes from Form 7205, so the work is on that form, not on Schedule C.
Where the number comes from: line 27b
The instructions for Part V say to “Enter the total on lines 48 and 27b.” Line 27b is therefore a copy of the Part V total, which is built on the Schedule C Part V page. The same summary of changes says the Part V expense “is now reported on line 27b.”
Lines 28 and 29: no separate instruction paragraph
The instructions give no separate paragraph for lines 28 and 29, so the form’s own captions are the rule. Before line 28, Part II carries a capitalization rule: “Reduce the amounts on lines 8 through 27a and Part V by amounts capitalized.” That rule applies when “you produced real or tangible personal property or acquired real or personal property for resale, you must generally capitalize certain expenses in inventory or other property.” Gross income on line 7 comes from Part I, which is explained at Schedule C lines 2 to 5 and the pages near it.
As an illustration, not an IRS example: if line 7 is $50,000 and line 28 is $32,000 then line 29 is computed as $50,000 minus $32,000 which is $18,000. A negative result would be a tentative loss.
Where it goes next
Line 29 is the starting point for lines 30 to 32. Line 31 is captioned “Net profit or (loss). Subtract line 30 from line 29.” The instructions for line 32 begin “You don’t need to complete line 32 if line 7 is more than the total of lines 28 and 30.” Home office expense is the subject of Schedule C line 30, and the net profit or loss is covered at Schedule C lines 31 and 32.
Edition and line numbers
This page reads the 2025 Schedule C (Form 1040) and its 2025 instructions, the current files irs.gov served on 2026-10-18. They are byte-identical to the archived copies and they are the files for the tax year 2025 return, filed in 2026. The schedule says “Attach to Form 1040, 1040-SR, 1040-SS, 1040-NR, or 1041”; “partnerships must generally file Form 1065.” Schedule C has its own instructions booklet, titled “Instructions for Schedule C” (Form 1040). Check the tax year printed on the schedule you are filling in and use the line numbers on that year’s schedule, because a different year’s schedule can number or word its lines differently.
Common mistakes
- Putting home office costs into the expense lines. The Part II heading says “Enter expenses for business use of your home only on line 30.”
- Keeping an expense on its own line and again in Part V. The instructions say to “Enter the total on lines 48 and 27b.” and Part V is for expenses not deducted elsewhere.
- Skipping the capitalization reduction. The instructions say “Reduce the amounts on lines 8 through 27a and Part V by amounts capitalized.”
Related: Schedule C (Form 1040), Form 1040, and Form 1040 line by line.
Sources
- Instructions for Schedule C (Form 1040), Profit or Loss From Business (2025): https://www.irs.gov/pub/irs-pdf/i1040sc.pdf
- Schedule C (Form 1040), Profit or Loss From Business (2025): https://www.irs.gov/pub/irs-pdf/f1040sc.pdf
Read from the IRS documents linked above on October 18, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.