In order to claim Foreign Tax Credit on your US Federal Tax Return you must be paying taxes in a country that has a Double Taxation Agreement (DTA) with the United States. Currently, the DTA is with the United Kingdom – not Scotland. This means that should Scotland choose yes on 18th September, a new DTA would have to be agreed with Scotland. It would have to be agreed in the interim period.
If no DTA is established until the actual day of independence, it would be possible that an American citizen living in Scotland could pay tax twice on the same income.
At the moment we can only speculate that may happen should the people of Scotland chose to be independent.
US Citizens are taxed on worldwide income no matter where they live. If you have been living in Scotland and have been receiving income in Scotland (an no income from the USA) you may be required to prepare a US Tax Return. You can claim the tax deducted from your salary as a Foreign Tax Credit to reduce your liabilities to the IRS.
If you are a US citizen living in Scotland and would like to discuss this, please do not hesitate to contact us at firstname.lastname@example.org. We look forward to hearing from you.