U. S. citizens working abroad are subject to special income tax regulations. The following publication describes them in some detail. For legal advice or technical questions, rely on a qualified attorney or a tax specialist.

Tax Guide for U.S. Citizens and Resident Aliens Abroad; for use in preparing .... returns.  Washington, D.C.: Internal Revenue Service. Publication 54. Issued annually.
Perkins Public Documents  US Documents T22.44/2:54/
This publication discusses the special tax rules for U.S. citizens and resident aliens who work abroad, or who have income earned in foreign countries. The foreign earned income exclusion, the foreign housing exclusion, and the foreign housing deduction are explained.