Can I be resident in two countries in the same year?
Yes, and it is more common than people expect. Each country applies its own domestic residence rules, and those rules can both be satisfied at once — you keep a home and family ties in one country while building a settled life in the other. The treaty does not stop that happening. It deals with the consequence, by applying a sequence of tie-breaker tests that assign you to one country for treaty purposes. The tests run in order, and the case is built around the first one that produces a clear answer on your facts.
Which country wins if I keep a home in both?
Having a home available in each country means the first test does not settle anything, so the analysis moves down the sequence to where your personal and economic life is actually centred. That is a question of evidence rather than argument. What matters is where the family lives day to day, where the children are registered for school, which health system covers you, where your bank and employment relationships sit, and how the year was actually spent. The answer is assembled from those records, not from a preference stated after the fact.
What documents do I need to prove where I really lived?
The documents that carry weight are the ones created at the time for their own purposes: leases and mortgage papers, school registrations, medical coverage, utility and phone accounts, employment records, and anything that shows where the family actually slept each week. A statement written years later carries very little, because it was written knowing what answer is wanted. Assemble the file while the year is current, keep it with the return, and the position can be supported if it is ever examined.
Do I have to file in both countries while residency is unresolved?
Usually yes. Each country's filing obligation comes from its own law, and it does not wait for the treaty question to be settled. The practical approach is to decide the treaty position first, then file consistently with it in both countries, disclosing the position where the return allows it. Filing one return as a resident and the other as though the first did not exist is what creates the contradiction that gets picked up later, because the two administrations can compare what you told each of them.
What happens if the tie-breaker tests do not resolve it?
Some cases are genuinely balanced, and running through the tests in order simply does not produce a winner. That is not a dead end. The treaty provides for the two tax administrations to settle the residence between themselves through the competent-authority route, and the outcome of that process becomes the position both returns follow. It is a formal application supported by the same contemporaneous evidence, so the work is not wasted. It is slower than a filing position, and it is the right route when the facts will not resolve on their own.
Can I just choose the country that suits me better?
No. The tie-breaker is a set of tests applied to facts, not an election you make on a return. Where there is real room, it comes earlier than the treaty: decisions about where the family lives, where a home is kept or given up, and when a move actually happens all change the facts the tests are applied to. Made in advance and documented as they happen, those choices shape the outcome. Presented afterwards as a preference, with nothing behind them, they do not.
Is my foreign pension taxable?
Usually in at least one country, and which one depends on the treaty article covering pensions — some give the taxing right to the country paying it, others to where you live, and several treat government service pensions differently again. Withholding at source is common and often reducible by treaty, with an elective return recovering an over-deduction. See the pensions article.
Does my foreign spouse have to pay US tax?
Not unless something connects them to the US system: they are a citizen or green card holder, they meet the substantial presence test, they have US-source income, or you elect to treat them as a US resident so you can file jointly. That election is the one people make without weighing it, because it reaches their foreign salary, their foreign investments and their foreign accounts, not just their name on the form. See a US person with a non-resident spouse.
