IRS Publication 538: Worked Examples for Calendar Year, Fiscal Year, Short Tax Year

Diving Into Publication 538: The Accounting Period Definitions

Publication 538 is structured around two big themes: accounting periods (which tax year you use) and accounting methods (cash vs. accrual). For foreign-owned LLC owners filing the pro forma 1120 + Form 5472, the accounting period chapters are the relevant ones.

Key definitions from the publication:

- **Calendar year**: 12 consecutive months beginning January 1 and ending December 31 - **Fiscal year**: 12 consecutive months ending on the last day of any month except December (or a 52–53 week tax year) - **Short tax year**: any tax year of less than 12 months

How You Adopt a Tax Year

You adopt a tax year by filing your first income tax return using that tax year. Filing an application for extension, employer ID number paperwork, or estimated tax doesn't establish a tax year. The first actual income tax return is the establishing act.

For a foreign-owned single-member LLC, this means: your first pro forma Form 1120 + Form 5472 effectively establishes your tax year. Whatever beginning and ending dates you enter on that first filing become your LLC's adopted tax year going forward.

Calendar Year Is the Default

For most people, the calendar year is the natural default — January 1 to December 31. Publication 538 confirms this is the standard 12-month tax year, the one most U.S. individuals and many entities use without thinking about it.

Foreign-owned LLCs almost always use the calendar year unless there's a specific reason to use a fiscal year (uncommon for single-member LLCs). The owner's home country tax year may or may not align with the U.S. calendar year, but the LLC's tax year is a separate decision from the owner's personal tax year.

Short Tax Year Trigger: Not Existing for the Entire Year

Publication 538 explicitly addresses the short tax year trigger: "A short period tax return may be required when you (as a taxable entity) are not in existence for the entire year, or you change your accounting period."

So if your entity didn't exist for the entire year (you formed it mid-year, or dissolved it mid-year), a short period tax return is required. The general rule: even when an entity wasn't in existence for the entire year, a return is still required for the time it WAS in existence. Filing requirements and tax computations are generally the same as for a full tax year ending on the last day of the short period.

Worked Example from Publication 538

Publication 538 provides a classic worked example:

"XYZ Corporation was organized on July 1 and elected a calendar year as its tax year. The corporation's first return will cover the short period from July 1 through December 31."

That's the formation scenario. The mirror example for dissolution:

"A calendar year corporation that dissolved during the year — the final return will cover the short period from January 1 through the date of dissolution (e.g., July 23)."

Both examples follow the same rule: enter the actual beginning and ending dates of the entity's existence during the tax year. The IRS has no special form for short tax years — you use the same Form 1120, just with shorter date ranges in the tax-year fields.

Why Foreign Owners Should Know This

For foreign owners forming their first U.S. LLC, the short tax year for the formation year is almost universal — entities are rarely formed exactly on January 1. So your very first pro forma 1120 + Form 5472 filing will likely be a short tax year filing.

Publication 538's worked example is the direct template: enter the formation date as the beginning, December 31 as the ending, check the "initial return" box, file by the next April 15 (or June 15 with foreign extension). Done.