To calculate business taxable income, start with your gross receipts from every source, subtract the cost of goods sold to get gross profit, subtract the ordinary and necessary expenses of running the business, remove any receipts the tax code excludes from income, and — if you own a pass-through entity — apply the qualified business income deduction. What remains is the figure your tax is calculated on, whether that tax lands on a corporate return or flows through to your personal 1040.
The Calculation, Step by Step
The math is the same regardless of entity type. The differences come in what qualifies for each line.
- Gross receipts: total revenue from sales, services, and every other income source.
- Minus cost of goods sold: direct production or acquisition costs for inventory. The result is gross profit.
- Minus operating deductions: rent, wages, insurance, utilities, depreciation, and other ordinary business expenses.
- Minus exclusions: items like loan proceeds or tax-exempt interest that should not have been counted as income in the first place.
- Minus the qualified business income deduction, if you qualify as a pass-through owner.
The number at the bottom is taxable income. A C-corporation pays a flat 21% federal tax on it.1Office of the Law Revision Counsel. 26 USC 11 – Tax Imposed A sole proprietorship, partnership, or S-corporation passes it through to the owners, who pay tax at their individual rates.
What the IRS Treats as Gross Income
The federal definition of gross income is deliberately wide. It includes all income from whatever source unless a specific provision excludes it.2Office of the Law Revision Counsel. 26 USC 61 – Gross Income Defined Sales revenue and service fees are obvious. Interest on a business bank account, rent on property you own, and royalties from licensed intellectual property all count too.
Barter trips up a lot of small businesses. If you trade services and no cash changes hands, the fair market value of what you received is still taxable income. A web designer who builds a site in exchange for $2,500 worth of legal work reports $2,500 of income, and so does the attorney.3Internal Revenue Service. Topic No. 420, Bartering Income The IRS treats barter exactly like a cash transaction.4Internal Revenue Service. Bartering and Trading? Each Transaction Is Taxable to Both Parties
Selling business assets is another line item that often gets missed. When you sell equipment, real estate, or inventory, each asset is treated separately. Inventory sales produce ordinary income. Equipment and real estate held longer than one year can produce a gain or a loss depending on the sale price compared with your adjusted basis in the property.5Internal Revenue Service. Sale of a Business
Deductions That Reduce Taxable Income
The federal tax code lets businesses deduct ordinary and necessary expenses paid while carrying on a trade or business.6Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses Ordinary means common in your industry. Necessary means helpful — not indispensable — to running the business. Personal expenses never qualify, and mixing personal and business spending is one of the fastest ways to draw an audit.
Cost of Goods Sold
If you manufacture or resell physical products, subtract cost of goods sold from gross receipts before anything else. This covers raw materials, direct production labor, and inbound shipping. What remains is your gross profit, and every other deduction comes off that number.
Operating Expenses
Rent for office or retail space, utilities, commercial insurance, employee wages, and the employer’s share of payroll taxes are the standard operating deductions. Documenting them properly matters as much as claiming them.
Depreciation, Section 179, and Bonus Depreciation
When you buy equipment, vehicles, or other long-lived assets, regular depreciation rules spread the deduction across the asset’s useful life. Two provisions can shortcut that.
The Section 179 deduction lets you write off the full purchase price of qualifying equipment and software in the year you place it in service. For 2026, the maximum deduction is $2,560,000, and the benefit begins phasing out once total qualifying purchases exceed $4,090,000. Bonus depreciation, made permanent at 100% by the One, Big, Beautiful Bill Act for property acquired after January 19, 2025, allows you to deduct the entire cost of qualifying assets in the first year with no dollar cap.7Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One, Big, Beautiful Bill For most small and mid-sized businesses, equipment purchases can now be expensed immediately.
Home Office
If you use part of your home regularly and exclusively for business, a portion of housing costs is deductible. The simplified method is $5 per square foot of dedicated office space, up to 300 square feet, for a maximum $1,500.8Internal Revenue Service. Simplified Option for Home Office Deduction The regular method applies your business-use percentage to actual mortgage interest, property taxes, insurance, and utilities. It requires more recordkeeping but usually produces a larger deduction.
Receipts That Are Not Taxable Income
Not every deposit in your business bank account is income. Several categories are excluded by statute, and treating them as taxable is a straight overpayment.
Loan proceeds are the most common example. When you borrow $100,000, you owe $100,000 back, so there is no net gain and no income. If any portion of that debt is later forgiven, the forgiven amount generally becomes taxable at that point.9Internal Revenue Service. Topic No. 431, Canceled Debt – Is It Taxable or Not?
Life insurance proceeds paid to a business on the death of a key officer or owner are excluded from gross income.10Office of the Law Revision Counsel. 26 USC 101 – Certain Death Benefits
Interest on state and local government bonds is generally exempt from federal income tax.11Office of the Law Revision Counsel. 26 USC 103 – Interest on State and Local Bonds If your business holds cash reserves in municipal bonds, the interest earned does not add to taxable income.
Cash or Accrual: When a Dollar Counts
Your accounting method decides when revenue and expenses hit the calculation. Under the cash method, income is reported when payment is received and expenses when they are paid. Under the accrual method, income is reported when earned and expenses when incurred, regardless of cash movement. That timing difference can shift thousands of dollars between tax years.
Most small businesses use cash accounting because it is simpler and matches real cash flow. A corporation or partnership whose average annual gross receipts over the prior three years exceed a statutory threshold must generally use accrual.12Office of the Law Revision Counsel. 26 USC 448 – Limitation on Use of Cash Method of Accounting The threshold is $25 million, adjusted annually for inflation; the adjusted figure for 2023 was $29 million. If your business is anywhere near that line, run the three-year average before you file.
The 20% Deduction for Pass-Through Owners
Owners of sole proprietorships, partnerships, and S-corporations get a break C-corporations do not. The qualified business income deduction lets eligible taxpayers deduct up to 20% of qualified business income from a domestic business.13Internal Revenue Service. Qualified Business Income Deduction Originally set to expire after 2025, the deduction was made permanent by the One, Big, Beautiful Bill Act.
The full 20% is available without restriction if taxable income falls below $201,750 (or $403,500 on a joint return) for 2026. Above those thresholds, limits kick in based on the type of business, the W-2 wages the business pays, and the cost basis of its physical assets. The deduction phases out entirely at $276,750 for most filers and $553,500 for joint filers. Service businesses like law firms, medical practices, and consulting companies face the tightest restrictions once income crosses the lower threshold.
Where the Number Goes on Your Return
Taxable income does not sit still. It flows onto a specific form based on how your business is organized, and that form determines who writes the check.
A sole proprietor reports business income and expenses on Schedule C, attached to a personal Form 1040.14Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business (Sole Proprietorship) Net profit is taxed at individual rates. Partnerships file Form 1065 and issue each partner a Schedule K-1 with their share of income. S-corporations file Form 1120-S and issue K-1s the same way. In all three cases, the business itself pays no federal income tax; the owners do, on their personal returns.
C-corporations file Form 1120 and pay tax directly at 21%.1Office of the Law Revision Counsel. 26 USC 11 – Tax Imposed When after-tax profits are distributed as dividends, shareholders pay tax on them again. That is the double taxation that makes the C-corporation structure less attractive for smaller businesses.15Internal Revenue Service. Forming a Corporation
One boundary worth flagging: for sole proprietors and general partners, taxable business income also triggers self-employment tax, which funds Social Security and Medicare at a combined 15.3% rate.16Office of the Law Revision Counsel. 26 USC 1401 – Rate of Tax That tax is calculated on 92.35% of net business profit and is separate from the income tax calculation above, not part of it.
When the Business Loses Money
If deductions exceed income, the result is a net operating loss. Losses generated in tax years beginning after 2020 cannot be carried back, but they can be carried forward indefinitely. Carried-forward losses can offset only up to 80% of taxable income in the year they are applied, so at least 20% of that year’s income remains taxable regardless of accumulated losses. Farming operations are an exception and can still carry losses back two years.
Non-corporate taxpayers face an additional cap. In 2026, net business losses exceeding $256,000 ($512,000 on a joint return) cannot offset other income like wages or investment gains. The excess becomes a net operating loss carryforward for the following year.