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Guide · Schedule C
Home office deduction in Excel
If you qualify for a home office write-off, Excel will not file Form 8829 for you — but a clean square-footage note plus an expense log makes March less painful. This is a practical recordkeeping guide, not tax, legal, or accounting advice.
Two common methods (high level)
| Method | What you track in a sheet | Best when |
|---|---|---|
| Simplified | Qualified office sq ft × IRS rate (subject to caps) | Smaller exclusive space; less paperwork |
| Regular | % of rent/mortgage interest, utilities, insurance, repairs allocable to the office | Larger space or actual costs clearly beat simplified |
Exclusive-use and principal-place-of-business tests still matter. Confirm current rules in IRS Pub 587 or with a preparer — kitchen tables that double as dinner usually fail exclusive use.
Minimum columns for either path
- Office sq ft and home sq ft (sketch or photo note helps)
- Method chosen for the year (simplified vs regular)
- Date range the space was exclusive business use
- Under regular: monthly rent/mortgage interest, utilities, internet, insurance, repairs — with a business %
- Link each row to a receipt/PDF filename in Notes
Yellow = your measurements and bill amounts.
Gray = % and running totals.
No macros.
Weekly / monthly habit
- Once a month, drop utility and rent PDFs into a folder named by year
- Enter allocable amounts in the expense log with a consistent “Home office” (or utility) category
- Do not invent new category labels mid-year
- At quarter-end, filter the log and compare against your sq-ft notes
Home office rows belong with other business expenses — miles still go in a mileage log, not the receipt sheet.
Common mistakes
- Claiming a space that is not exclusive (guest room that is also storage for family)
- Mixing personal grocery runs into the same category as office utilities
- Changing the business % every month without a reason documented in Notes
- Waiting until tax software asks for Form 8829 inputs with no source sheet
Record-keeping only — not tax advice. Confirm deductible treatment with IRS.gov or a preparer.