A tax entity is any person, business, trust, or organization that the IRS recognizes as a separate unit for calculating, reporting, or paying federal income tax. The classification decides which return you file, what rate applies, and whether the same dollar of profit gets taxed once or twice on its way to a person’s pocket. Federal tax law sorts these entities into five working categories: pass-through entities, C corporations, fiduciary entities, disregarded entities, and tax-exempt organizations.
Pass-Through Entities
A pass-through entity does not pay federal income tax itself. Income, losses, deductions, and credits flow directly to the owners’ personal returns and are taxed at individual rates. That single layer of tax is why the pass-through structure is the default choice for most small businesses.
Three structures dominate this category:
- Sole proprietorships report business results on Schedule C of Form 1040. There is no separate business return; the owner adds the profit or loss to everything else earned that year.1Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss from Business
- Partnerships file Form 1065 as an information return but owe no income tax at the entity level. Each partner receives a Schedule K-1 showing their share of the results and carries those numbers onto their own 1040.2Internal Revenue Service. About Form 1065, U.S. Return of Partnership Income
- S corporations file Form 1120-S and issue K-1s the same way partnerships do. The company-level return is informational only.3Internal Revenue Service. About Form 1120-S, U.S. Income Tax Return for an S Corporation
Partnerships and S corporations file before individuals so their K-1s reach owners in time. For the 2025 tax year, Forms 1065 and 1120-S are due March 16, 2026 (moved a day because the usual March 15 falls on a Sunday), and individual returns are due April 15, 2026. Either entity can request an automatic six-month extension by filing Form 7004 on or before that March 16 deadline.
S Corporation Eligibility
S corporation status is not open to every business. The corporation must be domestic, have no more than 100 shareholders, and limit its shareholders to individuals and certain trusts. Partnerships, other corporations, and nonresident aliens cannot hold shares. The corporation can issue only one class of stock, though voting rights within that class can vary. Certain financial institutions, insurance companies, and international sales corporations are excluded regardless. All shareholders must sign Form 2553 to make the election.4Internal Revenue Service. S Corporations Break any of these rules later and the corporation loses pass-through treatment and reverts to C corporation taxation.5Office of the Law Revision Counsel. 26 USC 1361 – S Corporation Defined
The Qualified Business Income Deduction
Pass-through owners have access to a tax break corporate shareholders do not. The Section 199A qualified business income deduction lets eligible taxpayers deduct up to 20% of qualified business income from pass-through entities. Originally set to expire after 2025, it was extended into 2026 with income thresholds adjusted for inflation. Owners above the thresholds face additional limits tied to wages paid and depreciable property held by the business.
C Corporations
A C corporation is the opposite of a pass-through. It files its own return on Form 1120, calculates its own taxable income, and pays its own tax.6Internal Revenue Service. About Form 1120, U.S. Corporation Income Tax Return The federal corporate rate is a flat 21% of taxable income.7Office of the Law Revision Counsel. 26 USC 11 – Tax Imposed The corporation’s tax bill is entirely separate from what its shareholders owe personally.
The catch is double taxation. The corporation pays 21% on its profits. When it distributes those after-tax profits as dividends, shareholders pay again on the same money. Qualified dividends are taxed at long-term capital gains rates of 0%, 15%, or 20% depending on the shareholder’s income. Even at the 15% rate, a dollar of corporate profit that gets distributed loses roughly 33 cents between the two layers. That arithmetic explains why so many small businesses choose a pass-through structure instead.
The corporate form makes more sense when the business plans to reinvest most of its profits rather than distribute them, or when it needs to raise capital from a broad group of investors. A flat 21% can also come in below the top individual rate of 37%, giving corporations a timing advantage on retained earnings. But the second layer hits the moment money leaves the corporate treasury.
Fiduciary Entities: Trusts and Estates
Trusts and estates are tax entities in their own right, separate from the people who created them and from the beneficiaries who eventually receive the money. A fiduciary (a trustee or executor) files Form 1041 to report income earned by assets held inside the entity.8Internal Revenue Service. About Form 1041, U.S. Income Tax Return for Estates and Trusts Estates must file when gross income reaches $600 or more, and trusts must file when they have any taxable income or gross income of $600 or more.9Internal Revenue Service. Instructions for Form 1041 and Schedules A, B, G, J, and K-1
Who pays the tax depends on what happens to the income. Money that stays inside the entity is taxed to the entity. Money distributed to beneficiaries gets reported on their individual returns, with each beneficiary receiving a K-1 for their share.10Internal Revenue Service. Instructions for Form 1041 and Schedules A, B, G, J, and K-1 – Section: Purpose of Form
Trust and estate brackets are compressed hard. For 2026, the 37% top rate begins at just $16,000 of taxable income.11Internal Revenue Service. 2026 Form 1041-ES An individual would not hit that rate until well past $600,000. When the trust document allows it, distributing income to beneficiaries almost always produces a lower total tax.
Disregarded Entities
A disregarded entity exists under state law but is invisible for federal income tax purposes. The most common example is a single-member LLC. The IRS treats the LLC’s activity as if the owner conducted it personally, so there is no separate business tax return. If the owner is an individual, the numbers land on Schedule C of Form 1040, exactly like a sole proprietorship.12Internal Revenue Service. Single Member Limited Liability Companies
This differs from a partnership or S corporation in one important way. There is no entity-level information return linking the business to its owner. A partnership files Form 1065. An S corporation files Form 1120-S. A single-member LLC files nothing at the entity level for income tax purposes.
The Payroll Tax Exception
The “disregarded” label has a significant exception. For employment tax purposes, a single-member LLC is treated as a separate entity. If the LLC has employees, it must obtain its own EIN and file and pay employment taxes under the LLC’s name, not the owner’s. This rule has been in effect since January 1, 2009.12Internal Revenue Service. Single Member Limited Liability Companies The same LLC is invisible for income tax and visible for payroll tax. In practice, most single-member LLCs with workers need their own EIN even though they do not file a separate income tax return.
Tax-Exempt Organizations
Nonprofits are tax entities too, and generally exempt from federal income tax on activities tied to their mission. The most familiar designation is 501(c)(3), which covers organizations operated for charitable, religious, educational, scientific, or similar purposes. A qualifying organization must be organized exclusively for exempt purposes, must not distribute profits to insiders, and must stay out of political campaigns for or against candidates.13Internal Revenue Service. Exemption Requirements – 501(c)(3) Organizations
Tax-exempt does not mean filing-exempt. Most exempt organizations file an annual information return, with the specific form set by size:14Internal Revenue Service. Form 990 Resources and Tools
- Form 990 is required when gross receipts reach $200,000 or more, or total assets reach $500,000 or more.
- Form 990-EZ is available to smaller organizations below both of those thresholds.
- Form 990-N (the e-Postcard) is a simplified electronic notice for organizations with gross receipts normally $50,000 or less.
- Form 990-PF is required for all private foundations regardless of size.
Exempt organizations can still owe tax on income from activities unrelated to their mission. A charity that regularly runs a side business that doesn’t advance its exempt purpose owes unrelated business income tax on the net income. A university bookstore selling textbooks is mission-related; the same store selling branded clothing to the general public may not be. The IRS looks at whether the activity is regularly carried on and whether it directly advances the exempt purpose.
Changing Your Entity Classification
Initial classification is not permanent. Under the “check-the-box” regulations, eligible entities can elect a different federal tax classification by filing Form 8832.15Internal Revenue Service. Entity Classification Election (Form 8832) An LLC with two owners defaults to partnership treatment but can elect corporate taxation. A single-member LLC defaults to disregarded status but can also elect to be taxed as a corporation.
Switching has practical limits. Once you make a classification election, you generally cannot change again for 60 months. A newly formed entity’s initial election does not start that clock. Entities that want S corporation treatment skip Form 8832 and file Form 2553 instead.
The election can take effect no earlier than 75 days before the filing date and no later than 12 months after it. Miss those windows and you’ll need late election relief under the applicable revenue procedures, which requires demonstrating reasonable cause for the delay.
Employer Identification Numbers
Every tax entity needs an identifier for its dealings with the IRS. For most businesses, trusts, and estates, that identifier is an Employer Identification Number, a nine-digit number that functions like a Social Security number for the entity. You apply on Form SS-4.16Internal Revenue Service. About Form SS-4, Application for Employer Identification Number (EIN) Sole proprietors without employees can use their personal Social Security number, but any entity that hires workers, operates as a partnership or corporation, or files certain tax returns needs its own EIN.
The application asks for the entity’s legal name, a responsible party, and the entity type being formed. Getting the entity type right on the application matters because it determines the filing category the IRS assigns. Online applications typically produce an EIN immediately; mail and fax applications take longer. Once issued, the EIN becomes the permanent reference point for every interaction with the agency.