What this line means
Your tentative profit from the business that uses your home, pulled directly from Schedule C, line 29. This number is the ceiling for most of your home office deductions. If your tentative profit is $5,000, you cannot deduct more than $5,000 in home office expenses (except for mortgage interest and real estate taxes, which are deductible regardless). The home office deduction cannot create or increase a business loss — it can only reduce your profit to zero.
Does this apply to you?
- You file Schedule C for a sole proprietorship and claim the home office deduction
- You need to determine how much of your home expenses are actually deductible this year
- You had a low-profit or break-even year and want to know if your home office deduction is limited
Easy to overlook
The profit limit does not kill your deduction — it delays it If your tentative profit is too low to absorb all your home office expenses, the excess carries forward to next year on line 43. You do not lose the deduction permanently. Filers in early-stage businesses with high startup costs and low revenue often assume they are wasting the home office deduction, but the carryover mechanism preserves it. 1 IRS Form 8829 instructions — Line 8
Mortgage interest and real estate taxes bypass this limit Even if your tentative profit is zero, you can still deduct the business portion of mortgage interest and real estate taxes. These deductions are allowed regardless of the profit limit because you would be able to deduct them anyway (on Schedule A, if you itemize). The profit limit on line 8 only constrains other expenses like utilities, insurance, and depreciation. 2 IRS Publication 587 — deduction limit based on gross income from business use
Watch out for this
Entering the wrong Schedule C line. Line 8 pulls from Schedule C, line 29 — which is tentative profit before the home office deduction. Do not use Schedule C, line 31 (net profit after home office), because that number already includes the deduction you are trying to calculate. Using line 31 creates a circular reference that understates your available deduction.
Footnotes
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IRS Form 8829 Instructions, Line 8. https://www.irs.gov/instructions/i8829 ↩
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IRS Publication 587, Business Use of Your Home, Deduction Limit. https://www.irs.gov/pub/irs-pdf/p587.pdf ↩