All businesses except partnerships must file an annual income tax return. Partnerships file an information return. The form you use depends on how your business is organized. Refer to Business Structures to find out which returns you must file based on the business entity established.
The federal income tax is a pay-as-you-go tax. You must pay the tax as you earn or receive income during the year. An employee usually has income tax withheld from his or her pay. If you do not pay your tax through withholding, or do not pay enough tax that way, you might have to pay estimated tax. If you are not required to make estimated tax payments, you may pay any tax due when you file your return.