Home costs for a home office belongs on Line 30, line 30, business use of your home.
Why line 30
The business share of your home costs is computed on Form 8829 and carried to line 30, below the Part II expense total. The standard allocation is area: the square footage used regularly and exclusively for the business divided by the total square footage of the home. Comparing the number of rooms is acceptable only where the rooms are about equal in size. The split then applies to indirect costs, rent or mortgage interest, insurance, utilities, general repairs, while a direct cost that benefits only the office, repainting that room for instance, is allocated to the business in full. What you need to prove is the measurement, which is why a dimensioned floor plan is the single most useful record here.
Log it once, with the line already on it. Type an expense in plain words in ClaryBook and it is filed with a date, vendor, amount and what it was for, so the number your preparer needs for home costs for a home office is already written down.
Start for freeWhat home costs for a home office is confused with
- Line 20b, rent or lease of other business property
- Rent paid for separate premises is line 20b in full, with no allocation, so an outside studio is a different computation entirely from a room at home.
- Schedule A, schedule a, personal itemised deduction
- The non-business share of mortgage interest and real estate taxes stays available on Schedule A if you itemise, so one bill splits between Form 8829 and Schedule A and must not be counted twice.
- Line 21, repairs and maintenance
- A repair to a separate business property is line 21 in full, while a repair to the whole house is an indirect home cost allocated by percentage on Form 8829.
Examples that belong on line 30
- 150 square foot office in a 1,500 square foot home: 10% business use
- $2,000 a month rent at 10%: $200 a month of indirect expense
- $2,400 annual utilities at 10%: $240 indirect
- $180 to repaint the office only: a direct expense, 100% allocated
- A 300 square foot room used half for work and half as a guest room: fails exclusive use, so no part of it counts
What does not belong here
- Including space that is not used regularly and exclusively for the business.
- Allocating by rooms when the rooms are plainly different sizes.
- Counting the same mortgage interest on both Form 8829 and Schedule A.
- Home rent on line 20b instead of Form 8829.
The limit that applies
The line 30 deduction is capped by the gross income limit on Form 8829 and amounts blocked by that cap carry forward. The simplified method replaces the whole allocation with a flat rate per square foot on up to 300 square feet.
What to keep
Keep a floor plan with the office dimensions and the total area, photographs of the room set up for work, and the year's rent or mortgage statements, utility bills and insurance. The dated floor plan with measurements is what makes the percentage a fact rather than an assertion.
Other expenses on line 30
Related lookups
- Where does office rent go on Schedule C?
- Where does state income tax go on Schedule C?
- Where does a laptop repair go on Schedule C?
Sources
This page explains how Schedule C lines work. It is general information, not tax advice for your situation. If an expense is large or the answer turns on a fact about your business, confirm it with your tax preparer.
Looking for a different expense? The full Schedule C line lookup has every line from 8 to 27 with the expenses that belong on each, and Schedule C expense categories walks the whole form in order.
Log it once, with the line already on it. Type an expense in plain words in ClaryBook and it is filed with a date, vendor, amount and what it was for, so the number your preparer needs for home costs for a home office is already written down.
Start for free