Business Expenses

The ordinary and necessary test and how the IRS applies it on audit

Under IRC Section 162(a), a trade or business expense is deductible if it is both ordinary and necessary. The Supreme Court defined "ordinary" in Welch v. Helvering (1933) as an expense that is normal, usual, or customary in the taxpayer's line of business — not one that is unique or extraordinary. "Necessary" was defined more broadly: an expense is necessary if it is appropriate and helpful to the business, even if it is not strictly indispensable. These are objective standards measured against what other businesses in the same trade typically spend, not against the specific taxpayer's subjective belief.

The IRS examines Schedule C deductions by looking at the nature of the expense, its connection to the taxpayer's specific business activity, and whether the amount is reasonable. Under Treas. Reg. Section 1.162-1(a), the expense must also be paid or incurred during the taxable year and must be directly connected to the conduct of a trade or business. Capital expenditures (assets with a useful life substantially beyond the taxable year) are not currently deductible under Section 162 but may be recovered through depreciation under Section 168 or immediately expensed under Section 179 or 100% bonus depreciation under Section 168(k), which OBBBA made permanent.

A common area of confusion is the distinction between business expenses and personal expenses. IRC Section 262 flatly disallows deductions for personal, living, or family expenses. When an expense has both business and personal elements — such as a cell phone used for both business and personal calls — you must allocate the expense between business and personal use based on actual usage records. The IRS does not accept estimates without supporting documentation. On audit, the burden of proof is on the taxpayer under IRC Section 6001 to substantiate every deduction claimed, and under Section 274(d), certain categories (travel, entertainment, gifts, listed property) require heightened substantiation with contemporaneous records.

A business expense must be ordinary (common in your trade) and necessary (helpful to your business) to be deductible. Personal expenses are never deductible. (IRC §162(a); IRC §262; Treas. Reg. §1.162-1(a); IRC §274(d))

De minimis safe harbor and Section 179 expensing: immediate deductions for business assets

Under Treas. Reg. Section 1.263(a)-1(f), the de minimis safe harbor allows businesses without an applicable financial statement to expense items costing $2,500 or less per invoice (or per item) rather than capitalizing and depreciating them. You must make the election annually by attaching a statement to your tax return, though in practice this is done by reporting the expenses on Schedule C. This is enormously valuable for tradespeople and service businesses that frequently purchase tools, equipment, and supplies in the sub-$2,500 range. A $2,200 laptop, a $1,800 set of diagnostic tools, or a $900 pressure washer can all be fully deducted in the year of purchase under this safe harbor.

For assets exceeding the de minimis threshold, IRC Section 179 allows you to elect to expense the cost of qualifying tangible personal property, off-the-shelf computer software, and certain improvements to nonresidential real property in the year placed in service rather than depreciating over multiple years. For 2026, the Section 179 deduction limit is $2,560,000, with a phase-out beginning at $3,200,000 in total qualifying property placed in service. The deduction cannot exceed taxable income from the active conduct of a trade or business. Qualifying property includes machinery, equipment, furniture, most software, and certain qualified improvement property. Vehicles have separate limits: $12,400 for passenger automobiles under the luxury auto limits, or the full cost for vehicles over 6,000 lbs GVWR that are used more than 50% for business.

In addition to Section 179, OBBBA made 100% first-year bonus depreciation permanent under IRC Section 168(k). This applies automatically to new and used qualifying property with a recovery period of 20 years or less. Unlike Section 179, bonus depreciation is not limited by taxable income and can create or increase a net operating loss. For most sole proprietors, the combination of the de minimis safe harbor, Section 179, and 100% bonus depreciation means that virtually all business asset purchases can be deducted in full in the year of purchase.

Items costing $2,500 or less can be expensed immediately under the de minimis safe harbor. Larger assets can be fully deducted under Section 179 (up to $2,560,000 for 2026) or 100% bonus depreciation. (Treas. Reg. §1.263(a)-1(f); IRC §179; IRC §168(k); OBBBA §179 limit $2,560,000)

Home office deduction: the simplified method vs the regular method

The home office deduction under IRC Section 280A allows self-employed individuals to deduct expenses for the business use of their home, provided the space is used regularly and exclusively as the principal place of business, as a place to meet clients, or as a separate structure used in connection with the trade or business. The "exclusive use" requirement is strict: a spare bedroom used as both an office and a guest room does not qualify, even if the business use is predominant. The only exception to exclusive use is for storage of inventory or product samples if the home is the sole fixed location of the business, and for a licensed daycare facility.

The simplified method, introduced in Revenue Procedure 2013-13, allows a deduction of $5 per square foot of home office space, up to a maximum of 300 square feet ($1,500 maximum deduction). This eliminates the need to track actual home expenses and calculate the business-use percentage. The simplified method is attractive for its ease of compliance, but it caps your deduction at $1,500 regardless of actual costs. If you live in a high-cost area or your home expenses are substantial, the regular method almost always produces a larger deduction.

The regular method requires you to calculate the business-use percentage of your home (typically office square footage divided by total home square footage) and apply that percentage to actual home expenses. Deductible expenses fall into two categories: direct expenses (those that benefit only the office, such as painting the office or installing dedicated business internet) are 100% deductible, while indirect expenses (mortgage interest or rent, utilities, insurance, repairs, depreciation on the home itself) are deductible based on the business-use percentage. Under the ordering rules of Section 280A(c)(5), the deduction cannot exceed the gross income from the business activity conducted in the home, minus the deductions allocable to the activity regardless of the home office (such as business supplies and advertising). Any excess can be carried forward to future years.

For homeowners using the regular method, the depreciation component can be significant. You depreciate the business-use portion of the home's basis (cost minus land value) over 39 years using the straight-line method. When you sell the home, the depreciation claimed (or allowable) must be recaptured as ordinary income under Section 1250, even if the gain is otherwise excluded under the Section 121 home sale exclusion. This recapture trap is often overlooked and should factor into the decision between the simplified and regular methods.

The home office deduction requires regular and exclusive business use. The simplified method provides $5 per square foot up to $1,500. The regular method allows a percentage of actual home expenses but requires more documentation. (IRC §280A; Rev. Proc. 2013-13; IRC §280A(c)(5); IRC §1250)

Vehicle expenses, meals, and start-up costs: the deductions that trip up the most filers

Vehicle expenses are one of the most audited Schedule C deductions. You have two methods: the standard mileage rate (72.5 cents per mile for 2026) or the actual expense method (gas, insurance, repairs, depreciation, tolls, parking, prorated by business-use percentage). You must choose the standard mileage rate in the first year the vehicle is placed in service if you want to use it in subsequent years. Under IRC Section 274(d), you must maintain a contemporaneous written mileage log recording the date, destination, business purpose, and miles driven for each trip. Without this log, the IRS will disallow the entire vehicle deduction on audit — the Tax Court has consistently upheld disallowance for lack of contemporaneous records, even when the taxpayer could prove business use through other evidence (see Noz v. Commissioner, T.C. Memo. 2012-272).

Business meals are 50% deductible under IRC Section 274(n) when the meal is directly related to or associated with the active conduct of your business. You must document the amount, date, place, business purpose, and the name and business relationship of each person present. The temporary 100% deduction for restaurant meals (2021-2022) has expired; the rate is permanently 50% for 2023 onward. Entertainment expenses remain entirely nondeductible under TCJA Section 13304, with narrow exceptions for recreational activities primarily for the benefit of employees other than highly compensated employees.

Start-up costs under IRC Section 195 deserve special attention. If you launched your business during the tax year, you can deduct up to $5,000 of start-up costs immediately, reduced dollar-for-dollar by the amount your total start-up costs exceed $50,000. The remainder is amortized over 180 months (15 years) beginning with the month the active trade or business begins. Start-up costs include market research, travel to prospective business locations, advertising for the opening of the business, wages paid to employees being trained before operations begin, and professional fees for setting up the business. Investigatory costs (researching whether to enter a business) are also treated as start-up costs if you actually start the business. If you investigate but decide not to start, these costs are nondeductible personal expenses.

Vehicle expenses require a contemporaneous mileage log. Meals are 50% deductible with documentation of business purpose. Start-up costs are deductible up to $5,000 immediately with the excess amortized over 180 months. (IRC §274(d); IRC §274(n); IRC §195; TCJA §13304)