If I work in a foreign country for a few weeks as a consultant to a US company for a US employer and live in California, do I need report foreign income or anything else?

Yes. United States citizens and resident aliens are taxed on their worldwide income, whether the person lives inside or outside of the United States. However, qualifying U.S. citizens and resident aliens who live and work abroad may be able to exclude from their income all or part of their foreign salary or wages, or amounts received as compensation for their personal services. In addition, they may also qualify to exclude or deduct certain foreign housing costs.

A common misconception that contributes to the international tax gap is that this potentially excludable foreign earned income is exempt income not reportable on a US tax return. In fact, only a qualifying individual with qualifying income may elect to exclude foreign earned income and this exclusion applies only if a tax return is filed and the income is reported.

To claim the foreign earned income exclusion, the foreign housing exclusion, or the foreign housing deduction, you must have foreign earned income, your tax home must be in a foreign country, and you must be one of the following:

• A U.S. citizen who is a bona fide resident of a foreign country or countries for an uninterrupted period that includes an entire tax year,
• A U.S. resident alien who is a citizen or national of a country with which the United States has an income tax treaty in effect and who is a bona fide resident of a foreign country or countries for an uninterrupted period that includes an entire tax year, or
• A U.S. citizen or a U.S. resident alien who is physically present in a foreign country or countries for at least 330 full days during any period of 12 consecutive months.

Working in a foreign country for a few weeks would not qualify.