Blott,
Thanks for that. However even if you do meet the criteria for the aggregate 183 days in 3 years that does not mean you will automatically have to pay US tax. The same link gives the following exception
<blockquote id="quote" class="ffs">quote:Closer Connection to a Foreign Country
Even if you meet the substantial presence test, you can be treated as a nonresident alien if you:
Are present in the United States for less than 183 days during the year,
Maintain a tax home in a foreign country during the year, and
Have a closer connection during the year to one foreign country in which you have a tax home than to the United States (unless you have a closer connection to two foreign countries, discussed next).
Closer connection to two foreign countries. You can demonstrate that you have a closer connection to two foreign countries (but not more than two) if you meet all of the following conditions.
You maintained a tax home beginning on the first day of the year in one foreign country.
You changed your tax home during the year to a second foreign country.
You continued to maintain your tax home in the second foreign country for the rest of the year.
You had a closer connection to each foreign country than to the United States for the period during which you maintained a tax home in that foreign country.
You are subject to tax as a resident under the tax laws of either foreign country for the entire year or subject to tax as a resident in both foreign countries for the period during which you maintained a tax home in each foreign country.
Tax home. Your tax home is the general area of your main place of business, employment, or post of duty, regardless of where you maintain your family home. Your tax home is the place where you permanently or indefinitely work as an employee or a self-employed individual. If you do not have a regular or main place of business because of the nature of your work, then your tax home is the place where you regularly live. If you do not fit either of these categories, you are considered an itinerant and your tax home is wherever you work.
For determining whether you have a closer connection to a foreign country, your tax home must also be in existence for the entire current year, and must be located in the same foreign country to which you are claiming to have a closer connection.
Foreign country. In determining whether you have a closer connection to a foreign country, the term “foreign country” means:
Any territory under the sovereignty of the United Nations or a government other than that of the United States,
The territorial waters of the foreign country (determined under U.S. law),
The seabed and subsoil of those submarine areas which are adjacent to the territorial waters of the foreign country and over which the foreign country has exclusive rights under international law to explore and exploit natural resources, and
Possessions and territories of the United States.
Establishing a closer connection. You will be considered to have a closer connection to a foreign country than the United States if you or the IRS establishes that you have maintained more significant contacts with the foreign country than with the United States. In determining whether you have maintained more significant contacts with the foreign country than with the United States, the facts and circumstances to be considered include, but are not limited to, the following.
The country of residence you designate on forms and documents.
The types of official forms and documents you file, such as Form W–9, Form W–8BEN, or Form W–8ECI.
The location of:
Your permanent home,
Your family,
Your personal belongings, such as cars, furniture, clothing, and jewelry,
Your current social, political, cultural, or religious affiliations,
Your business activities (other than those that constitute your tax home),
The jurisdiction in which you hold a driver's license, and
The jurisdicti