Income Tax Laws for Expats
An assortment of questions have recently been asked about income tax obligations—U.S., Nicaragua and other countries—on the Casa Ben Linder mailing list. They are reasonable questions and it seems like something that would be of interest to a lot of NL members. Also, someone asked if they knew of any U.S. CPAs that lived here and could do people's U.S. taxes.
I am going to start off with what I know but there is clearly more. No, I am not an accountant or a tax lawyer. Toss in your answers.
Nicaragua Tax Law
There is no differentiation between Nicaraguans and ex-pats here. If you earn money in Nicaragua it is subject to income tax. I believe the rate is 30% but there are an assortment of exceptions (all the way down to 6%) to kiss the culo of various multinationals. Telecommunications, for example, is one of these exceptions.
The "loophole" here (and this is from a Nicaraguan accountant that works closely with La Renta is that if the money you are earning is not related to the Nicaraguan economy then, even though you are living in Nicaragua, it is not subject to tax in Nicaragua. For example, if you wrote a book for a U.S. publisher while living here, royalties from that work would not be taxable in Nicaragua.
Tax Law for Other Countries
There are two countries in the world (I have been told—I didn't check this) where your income is taxable in your home country no matter where it is earned. Those are the U.S. and the Philippines. If you are a citizen of any other country, the money you earn here is not taxable in your home country.
In the case of the U.S. there is a clause that may except you of some of that income. I believe the current number is around $90,000/year. Look up the details but the basic requirement is that you are not working for a U.S. company and that you spend at least 330 (or there abouts) days outside the U.S. during the work year.
Note that if you are a usano living in a foreign country, you have until June 15 to file your taxes. (This, in itself, would seem like an opportunity for a U.S.-based CPA to "vacation" in Nicaragua after April 15 and pick up some income doing taxes for ex-pats.)

If U.S.
Since the U.S. doesn’t have a “tax treaty” with most Latin countries (not necessary as taxes there are often handled differently), it is much easier than being in Europe, etc. U.S. Expats who meet the “Physical Presence Test” or the “Bona Fide Resident Test” may be able to utilize the “Foreign Earned Income Exclusion” and or the “Foreign Housing Exclusion”. The excluded income amount is adjusted each year (2006=$82,4k; 2007=$85,7k; 2008=$86,6k; etc.), using an inflationary formula. The “Bona Fide Resident Test” is actually rather strict, though few people assume this. This makes it one of the targets for audits (in 2001 I met someone who had handled these and she claimed at least one third of all people she ran into in C.A. who were claiming this did not qualify for it). Many people -perhaps quite honestly- claim it when they are not entitled to it. The primary question, with emphasis on “BONA FIDE”, “RESIDENT”, and “ENTIRE” is, “Were you a bone fide resident of a foreign country or countries for a period that includes the entire tax year?”. Many people claiming resident status are not residents or, even if they are, they often fail the time requirement (there are waivers on this, but personal circumstances don’t usually count and this is reserved for government work, civil unrest, war, etc. – and every Spring the IRS publishes a list of countries that quality due to adverse circumstances). Going somewhere for a year or more doesn’t make it your bona fide residence.
The second test is the “Physical Presence Test”. The tax form for foreign income exclusion includes a detailed chart of what days you were inside the U.S. The $86,6k exclusion presupposes you spent all 366 days outside the U.S., and all income derives from there (though you need a minimum of 330 days outside the U.S.); if you spent less than 366 days, then a formula comes into play and the exclusion amount decreases proportionately. Returning to the U.S. for any personal emergency/reason still counts toward the days not spent abroad. Due to past abuse, travel days spent in international waters or overnight in U.S. airport hubs on non-U.S. destination travel counts as U.S.-spent days, too. The monies above your exclusion amount are not your tax bracket, as is commonly done – and commonly audited (if you make $106,6k, then your tax bracket isn’t tied to the $20k difference, the amount above the exclusion, but $106,6k which is applied and paid on $20k – if that makes sense).
If your income was coupled with gratis housing, then that brings added concerns and complications – and there are special forms for determining this. Also included as earned income are pay differentials, overseas stipends, family allowances, educational equivalences, etc. Once you file excluded income, that exclusion remains in place until you revoke it, in writing. The June 15th due date is only if you qualify for “Automatic Extension-2” (I believe) – and there are requirements to this, so it is not as “automatic” as it might sound. There is also a 6-month automatic extension. But, these extend your time to file, not your time to pay (so interest comes into play on the unpaid tax amount). For income abroad, unless things just changed, the file date is an option depending on circumstances: April 15th if you are claiming a calendar-year tax, or 3 months and 15 days after the close of your fiscal year. If you make a good, comparable U.S.-based salary in C.A., it is sometimes in your interest to have a knowledgeable person due your taxes that first year, so you see how it is handled.