A US citizen who moved abroad mid-year and filed their first Form 2555 without counting their days correctly will recognize the problem immediately: the IRS denied the foreign earned income exclusion (FEIE) because they came up 12 days short of the 330-day threshold. The 330 day rule FEIE is a pure counting exercise, but the rules around what counts as a “full day,” which 12-month window you select, and how to document your presence are precise enough that errors like that one are far more common than they should be.
The physical presence test is one of two paths to the FEIE. The other is the bona fide residence (BFR) test, which requires establishing genuine residence in a foreign country for an uninterrupted period covering a full tax year. The 330 day rule FEIE asks only one question: were you physically present in one or more foreign countries for at least 330 full days during any period of 12 consecutive months that includes part of the tax year you are claiming? No residency intent, no visa category, no employment contract required. Only days.
What is the 330 day rule FEIE?
The IRS physical presence test requires at least 330 full days of physical presence in one or more foreign countries during any 12-consecutive-month period that includes some portion of the tax year at issue. Both US citizens and US resident aliens qualify; the test is time-based and entirely separate from immigration status, intent to reside, or any other subjective residency factor.
Tax home requirement and scope
Before any day abroad can count, you must have a tax home in a foreign country for the relevant period. The IRS defines your tax home as your regular or principal place of business (or, if none, your regular place of abode). Days spent outside the United States do not count toward the 330-day threshold if your tax home remains in the United States, regardless of how much foreign income you earn during those days. This is the provision that catches newly deployed contractors who keep their US apartment as their primary residence: the clock does not start until the tax home shifts offshore.
The 330 qualifying days do not need to be consecutive. You accumulate separate periods of presence across multiple foreign countries and they are aggregated across the selected 12-month window. A founder I advise spent three months in Singapore, two months in Portugal, four months in the UAE, and rounded out the remaining qualifying days across shorter stints in Japan and South Korea. Every day in each foreign country counted toward the same 330-day total, as long as the tax home was foreign throughout. Where a foreign tax home sits within a founder’s wider tax residency decisions across jurisdictions often determines whether the clock starts on day one of a move or months later.
Defining a “full day” and the counting rules
What counts as a full day
A full day under the IRS definition is a continuous 24-hour period beginning and ending at midnight spent within the territory of a foreign country, including its airspace and territorial waters. That definition has one immediate consequence: the day you depart the United States and the day you arrive back in the United States do not count, because neither day satisfies the full 24-hour requirement. If your flight leaves New York at 9 pm on March 1 and you land in London on March 2, only March 2 onward begins accumulating qualifying days.
What does not count
Time spent on or over international waters does not count as time in a foreign country and cannot be included in your 330-day count. Only periods when you are physically present on the territory of a foreign country qualify. Only territory within a recognized foreign country counts. There is no exception for illness, family emergencies, vacation in the United States, or employer orders: if you fall short of 330 full days in the 12-month period you selected, you do not meet the physical presence test, regardless of the reason. The IRS does not provide a hardship waiver under the statutory day-count rule.
That absence of relief is not a technicality. I have seen the consequences of misplaced confidence on this point: a client evacuated for a medical procedure spent six weeks recovering in the United States, pushed her count below 330, and lost the FEIE for that period entirely. She had no recourse. The only partial mitigation available is choosing a different 12-month window (covered below) that may still produce 330 qualifying days even accounting for the absence.
The 12-month period and flexibility
Custom 12-month windows
The 12-month period used for the physical presence test can begin on any day of any month and does not have to align with the calendar year. It must consist of exactly 12 consecutive months, ending the day before the same calendar date 12 months later. This flexibility is the most underused planning tool available to expats claiming the 330 day rule FEIE. By selecting the optimal rolling window, you can maximize the qualifying days that fall within the specific tax year you are claiming, even if your departure date mid-year would make a calendar-year window impossible.
Use our physical presence test calculator to model different start dates against your actual travel record before committing to a window on Form 2555.
Overlapping periods and strategy
Multiple overlapping 12-month periods may be used across different tax years. If Period A runs from April 1, 2024 to March 31, 2025, and Period B runs from October 1, 2024 to September 30, 2025, days from October 1 through March 31 appear in both windows. That is permitted. Days are counted only once per tax year for exclusion purposes, but the flexibility to select different periods for consecutive years allows you to cover partial-year departures and returns more precisely than a fixed calendar-year window permits.
The table below shows how three different 12-month window choices produce different qualifying day counts and exclusion claim years for a hypothetical expat who departed the United States on June 15, 2024:
| Window start | Window end | Qualifying days (est.) | Exclusion claim year |
|---|---|---|---|
| June 15, 2024 | June 14, 2025 | 365 (full window abroad) | 2024 and 2025 |
| July 1, 2024 | June 30, 2025 | 353 (excl. US return days) | 2024 and 2025 |
| January 1, 2025 | December 31, 2025 | 330+ (if no long US trips) | 2025 only |
The June 15 start date in the first row is the one that captures the 2024 partial year. Selecting January 1, 2025 as the window start abandons any 2024 FEIE claim entirely, which matters if you had significant foreign earned income in the second half of 2024. The 183-day rule works differently: it is a residency determination tool in most countries, not a US tax mechanism, and the 183-day rule across jurisdictions article explains how those two tests intersect for mobile founders holding both US obligations and foreign residency.
Documentation and Form 2555 filing
Form 2555 and Part III requirements
Claiming the FEIE under the physical presence test requires filing Form 2555, Foreign Earned Income, with your US individual income tax return. Part III of Form 2555 is where you specify your 12-month period, list your qualifying foreign days, and identify the countries in which you were present. The IRS does not accept a vague description: the form asks for exact dates and countries.
Expats who will not reach 330 days until after the regular April 15 filing deadline have one procedural option. Form 2350 (Application for Extension of Time to File US Income Tax Return) allows you to request an extension specifically to meet the physical presence test or BFR test requirements. This is a different form from the standard Form 4868 extension, and it exists precisely for this scenario.
Record-keeping and audit defense
Maintain contemporaneous records: passport stamps, flight boarding passes, travel itineraries, dated hotel receipts from foreign locations, and a day-by-day presence log. Day-counting errors are among the more frequent audit triggers for expats claiming the FEIE, and the IRS scrutinizes partial days and transit days closely. Records assembled after the fact from memory carry far less weight than records kept in real time.
A spreadsheet updated weekly, cross-referenced against passport entries and credit card records from foreign locations, is the standard I recommend to every client managing the physical presence count. The tax residency rules for expats in Singapore article is a useful reference for founders who are also managing a foreign country’s day-count requirement alongside the US test, since the two counting regimes interact in ways that a single-jurisdiction record often fails to capture.
FAQ
How is a “full day” defined for the 330 day rule FEIE, and do travel days to or from the US count?
A full day is a continuous 24-hour period beginning and ending at midnight spent within a foreign country’s territory. Travel days on which you depart from or arrive in the United States do not satisfy the 24-hour requirement and do not count. Time in international airspace or international waters during those journeys is also excluded.
Can I use any rolling 12-month window for the physical presence test, and how do overlapping periods work?
Yes. The 330 day rule FEIE allows you to select any 12-consecutive-month period that includes some part of the tax year you are claiming, with no requirement that the window align to the calendar year. Overlapping windows covering different tax years are permitted, so a period running from June 2024 through May 2025 can support a 2024 exclusion claim, and a separate period running from October 2024 through September 2025 can support a 2025 claim, with the overlapping days counted once per year. The choice of start date is a planning decision, not a fixed rule, and selecting the wrong window is the most common reason expats leave FEIE coverage on the table for partial-year departure years.
What happens if I fall short of 330 days due to illness, emergency, or employer orders?
Nothing in the statute excuses a shortfall. The IRS does not recognize any hardship waiver under the physical presence test: illness, family emergency, vacation in the United States, and employer recall are all treated identically. If you miss the 330-day threshold in your selected window, you do not meet the test for that period. The only available remedy is examining whether a different 12-month window, shifted to exclude the period of US presence, still produces 330 qualifying days while covering the tax year at issue. If no qualifying window exists, the bona fide residence test may be available as an alternative path to the FEIE, though that test has its own distinct requirements.
