A fiscal year is a concept that you will frequently encounter in finance. Many firms elect to use a different 12-month cycle than the one we are accustomed to, since the Internal Revenue Service gives tax-paying businesses such an option. Failing to take the differences between a fiscal and a calendar year into account can therefore result in accounting mistakes.


A calendar year is defined as January 1 through December 31. A fiscal year is any consecutive 12-month cycle that ends at the final day of any month.

Defining a Calendar Year

A calendar year is simply the conventional year that begins on January 1 and ends on December 31. Most businesses use the calendar year for financial calculations. If such a firm refers to its 2018 full-year profits, for example, it is talking about the total money it has earned between January 1, 2018, and December 31, 2018.

In the absence of an indication to the contrary, it is assumed that a firm uses the calendar year. However, to eliminate any possible confusion, the annual reports of most firms that use the calendar year will specifically state the beginning and end dates covered by the income statement, even if these days coincide with the beginning and end of the calendar year.

Defining a Fiscal Year

In finance, a fiscal year is a 12-month period that ends on the last day of any month. A fiscal year may end on April 30, for instance. Such a fiscal year would start on May 1 of the previous year, since it must cover 12 full consecutive months. For instance, the fiscal year of a firm that has ended on April 30, 2018, would have begun on May 1, 2017.

To find the start date of a fiscal year, add one day to the end date and then go back a full year. If the last day of a fiscal year is August 31, 2017, adding one day will take us to September 1, 2017. Going back a full year results in September 1, 2016, which is the start day of that fiscal year.

It makes sense to use a fiscal year that coincides with a complete business cycle for a business. For instance, a nursery school is likely to use a September 1 to August 31 year, rather than a January 1 to December 31 fiscal year.

The IRS and Taxation

The IRS allows businesses to chose any fiscal year they like, if the Internal Revenue Code and the Income Tax Regulations do not mandate a specific beginning and end date applicable to the firm. A business is generally mandated to use the calendar year if it does not keep books or records, which may be the case for self-employed individuals.

Switching to a Fiscal Year

If you have already filed an individual tax return using a calendar tax year and you start to operate as a business or sole proprietorship, begin to receive income from a partnership or acquire shares in an S corporation, you must continue to use the calendar year. Before you can switch to a fiscal year, you must first obtain IRS approval .

Tax filers who use a fiscal year must send their tax returns on the 15th day of the fourth month following the conclusion of their fiscal year. If, for example, your fiscal year ended on June 30, your tax filing deadline is October 15.