The Core Filing Mechanics
Cambodia and the US both run calendar-year tax systems, simplifying reconciliation. Without a tax treaty to lean on, Americans here rely entirely on domestic-law mechanisms, the FEIE and the Foreign Tax Credit, for double-tax relief.
Form 1040 and the Automatic Extension
The standard deadline is April 15, with an automatic extension to June 15 for Americans abroad. Tax owed still accrues interest from April 15, so estimate and pay by then if you expect a balance due. A further extension to October 15 is available on request (Form 4868).
Form 2555: The FEIE Workhorse
Most Cambodia-based salaries fall well under the FEIE cap. Form 2555 is the primary tool here, qualifying via the Physical Presence Test (330 days outside the US) or Bona Fide Residence Test (a full uninterrupted tax year).
Worked Example: A Phnom Penh NGO Salary
An American program officer at a Phnom Penh-based NGO earns $52,000 annually, paid in USD given the dollarized economy. She qualifies for the FEIE via Bona Fide Residence after her first full tax year, shielding her entire salary from US tax. Her Cambodian tax obligations depend on her specific NGO agreement, some aid workers operate under exemptions tied to their organization's registration, worth confirming directly rather than assuming standard employee tax rules apply.
FBAR: FinCEN Form 114
Required if combined foreign account balances, Cambodian bank accounts, investment accounts, exceed $10,000 USD at any point in the calendar year. Filed electronically, due April 15 with an automatic extension to October 15.
FATCA: Form 8938
A separate, higher threshold attached to your Form 1040: generally $200,000 in specified foreign assets at year-end (or $300,000 at any point) for a single filer abroad, doubled for married filing jointly.
Cambodian GDT Filing for Residents
If you're a Cambodian tax resident (182+ days present, or your principal abode is in Cambodia), you'll also owe local tax on worldwide income at progressive rates up to 20%, generally handled via employer withholding if you're on formal payroll, or self-declared if self-employed under a Patent Tax certificate.
Streamlined Compliance for Late Filers
If you've been in Cambodia for years without realizing citizenship-based US taxation still applied, the IRS Streamlined Foreign Offshore Procedures let you catch up on the last three years of returns and six years of FBARs without standard failure-to-file penalties, provided the omission was non-willful.