The tax form your business needs to file depends entirely on how your business is structured for tax purposes. Entity type determines the form, and using the wrong one can trigger rejections, penalties, or delayed refunds.

Sole proprietorships and single-member LLCs file Schedule C as part of your personal Form 1040. The business doesn’t file a separate return. All income and expenses flow directly onto your individual tax return. This is the simplest structure, but it still requires organized records to support every number on that schedule.

Partnerships and multi-member LLCs file Form 1065. This is an informational return, meaning the partnership itself doesn’t pay tax. Instead, each partner receives a Schedule K-1 showing their share of income, deductions, and credits. Each partner then reports their K-1 on their own personal return. The 1065 is due March 15, not April 15, and late filing penalties are $220 per partner per month.

S-Corporations file Form 1120-S. Like partnerships, S-Corps are pass-through entities that issue K-1s to shareholders. If your LLC elected S-Corp taxation by filing Form 2553 with the IRS, you file the 1120-S rather than Schedule C. This is one of the most common points of confusion. Your LLC might be registered with the state as an LLC, but if you made the S-Corp election, your business tax return is Form 1120-S.

C-Corporations file Form 1120. Unlike pass-through entities, C-Corps pay tax at the corporate level. Shareholders then pay tax again when profits are distributed as dividends. The C-Corp return is due April 15.

Nonprofits with tax-exempt status file Form 990, 990-EZ, or 990-N depending on their annual revenue. These are informational returns, but missing the filing deadline three consecutive years results in automatic loss of your exempt status.

The biggest source of confusion is LLCs. An LLC is a legal structure, not a tax classification. A single-member LLC defaults to sole proprietor treatment. A multi-member LLC defaults to partnership treatment. Either one can elect S-Corp or C-Corp taxation. The form you file follows your tax election, not what your state registration paperwork says.

For Florida businesses, there is no personal state income tax. Sole proprietors, partners, and S-Corp shareholders don’t file a state return for business income. C-Corporations may need to file a Florida Form F-1120 corporate income tax return if they meet the filing threshold.

If you’re unsure about your entity type or which election you made, check your IRS determination letters and formation documents. Getting business tax preparation help from someone who understands your situation prevents costly filing mistakes and makes sure you’re claiming everything available to you.