How do you count 330 days for the FEIE?

Key parameters
Days required	330
Window	Any 12 consecutive months
A "full day"	Midnight to midnight, entirely abroad
Days you can spend elsewhere	35 or 36

This is where counts go wrong. The FEIE physical presence test does not count days you were mostly abroad. A day counts only if you were in a foreign country for the whole 24 hours, midnight to midnight.

The consequences are concrete:

• Your departure day from the US usually does not count, because part of it was spent in the US or over international waters.
• Time on or over international waters is not time in a foreign country. A long ocean crossing can produce a day that belongs to nowhere and counts for nothing.
• Travel outside foreign countries lasting 24 hours or more costs you qualifying days for that period.

One narrow relief runs the other way: if you pass through the United States for less than 24 hours while travelling between two foreign points, you are not treated as present in the US during that transit.

With 330 required out of 365, the margin is 35 days — and travel days consume it faster than trips do.

The 12-month period is not the calendar year and not the tax year. It can begin on any day of any month, it does not have to start with your first full day abroad or end with the day you leave, and the IRS is explicit that you may choose the period giving the greatest exclusion.

That turns the count into an optimisation rather than a pass/fail: a window that fails 1 January to 31 December may comfortably pass if it starts in March. It also means the window can straddle two tax years, with the exclusion apportioned to each.

You cannot do that from memory. Finding the best 12 months requires knowing where you were on every day, because moving the start date by a week changes which days fall inside.

Two other conditions sit alongside it, and the day count does nothing for either:

• A foreign tax home is required. Someone who keeps their abode in the United States can hit 330 days and still not qualify.
• The exclusion covers earned income only. Pensions, dividends and capital gains stay taxable, and the amount excludable is capped annually.

The alternative route in — bona fide residence for an uninterrupted full tax year — is not a day count at all, and it suits people settled abroad better than the physical presence test does.

Which route is better, and how it interacts with foreign tax credits, is a question for a US tax adviser rather than a rule of thumb.

• IRS — Foreign earned income exclusion: physical presence test
• IRS — Foreign earned income exclusion
• IRS — Foreign earned income exclusion: tax home in a foreign country