The tax form for C corporation business entities is Form 1120. Form 1120a is the short form version. C corporations that file over 250 tax returns annually and/or have assets exceeding $10 million must file Form 1120 for years that ended on or after December 31, 2007. 

Overview of C Corporation Forms for Taxes

C corporations, also known as regular corporations, are taxed as a separate entity. The corporation must file Form 1120 annually to report income and claim its credits and deductions. The income earned by the C corp is normally taxed at the current corporate rate. 

For personal services corporations whose employees work in fields, such as engineering, accounting, law, health, actuarial science, consulting, or performing arts are taxed at a flat percentage rate of the net profits.

A C corporation's tax thresholds are not indexed for inflation the way they are for individual taxes. This only occurs through Congressional tax legislation.

Corporations pay income tax on business income at the business level, and any distributions to stockholders will be taxed again as dividends at the shareholder's individual tax rate. If any wages are paid to shareholders, these are also taxed on the shareholder's personal income tax return.

Although "double taxation" may cause small business owners to be concerned about incorporating, good tax planning can minimize the impact of the double taxation process. As an example, all corporate profits are not subject to double taxation. Operators of a corporation are allowed to withdraw reasonable salaries that are deducted from the corporation's profits. In this case, double taxation does not exist.

The corporation will want to ensure that all deductions available to the C corporation such as employee benefit plans, rent, charity donations, and compensation of officers are taken.

Along with filing and paying income tax, a C corporation has to pay employment taxes that include Medicare, Social Security, and unemployment taxes. For these, the corporation will use Form 940 and Form 941. Forms are available from the Internal Revenue Service website.

There are some states that require a franchise tax. The tax varies depending on the state where the company is registered as well as any states where the company does business that has a franchise tax. The franchise tax is not the same as business franchises.

Income Tax Rates and Due Dates

The tax rate tables through 2017 include a top corporate tax rate of 35 percent. The Tax Cut and Jobs Act of 2017 decreased the tax rate for corporations.

Corporations must file Form 1120 by the 3rd month, 15th day, after the end of the tax year for the corporation. If the tax year ends on December 31, the tax report is due by March 31. If that date falls on a holiday or weekend day, the report is due the following business day. 

Information About Form 1120

Section 1

  • The basic information needed for Form 1120 includes: The corporation name and address 
  • Employer ID Number (EIN)
  • Date the of incorporation
  • Total Assets.

Section 2

  • The corporation's income is broken down by category, which includes: Rents
  • Royalties
  • Interest
  • Capital gains
  • Gross receipts
  • Cost of goods.

Section 3

Corporations must have access to documentation of its expenditures if the business is audited. This includes: 

  • Compensation to officers
  • Other wages and salaries
  • Maintenance and repairs
  • Bad debts
  • Rents
  • Taxes and licenses
  • Interest expense
  • Charitable contributions
  • Depreciation (Form 4562)
  • Depletion
  • advertising
  • Pension, profit sharing, and other plans
  • Employee benefit programs
  • Domestic production activities (Form 8903) 
  • Other deductions outlined in the schedule.

Section 4

The corporation's refundable credits, tax, and payments are necessary; have documentation available for this section. Taxable income from the tax schedule less any credits provides whether the corporation receives a refund or has an amount due. 


  • Schedule A Cost of Goods Sold
  • Schedule C — Dividends and Special Deductions
  • Compensation of officers
  • Schedule J — Information on tax computation
  • Schedule K — includes information about the business type, NAICS classification number, stock, and shareholder information, etc.
  • Schedule L — Balance sheet per books for the beginning and end of the year
  • Reconciliation of Income/Loss per Books with Income Loss per Tax Return — Schedule M-1
  • Analysis of Partner's Capital Gains — Schedule M-2 — Unappropriated retained earnings per the books 

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