Could leaving a country on June 30 instead of July 1 actually change your tax situation? Sometimes. And that's the annoying little secret of international tax.
You can spend six months deciding where to move. You compare rent. Weather. Healthcare. Flights. Schools. Internet. Whether the local grocery store has decent coffee. Then tax law shows up and asks: "Great. What time did your flight leave?"
Suddenly your vacation itinerary is evidence. Your lease is evidence. Your family situation is evidence. Your bank account is evidence. Even the number of days you spent sleeping in a country can become important.
Because international tax doesn't just care about where you are. It can care about when you were there. And for Americans, this gets especially weird.
Because moving abroad generally does not turn off U.S. federal income taxation if you remain a U.S. citizen. The IRS says U.S. citizens and resident aliens abroad generally remain subject to U.S. income tax on worldwide income, although foreign tax credits, exclusions, treaties and other rules can affect the final result.
So your move isn't necessarily: America tax off, new country tax on. It can be: America tax still on, new country tax also on. Congratulations. You bought a one-way ticket and accidentally subscribed to two tax systems.