I have a question regarding renouncing U.S. citizenship and filing U.S. taxes.

I have a question regarding renouncing U. S. Citizenship and filing U. S. Taxes. I have used Person A and B for this example. June 4, 2014 â%u20AC%u201C Person A and B renounced their U. S. Citizenship at the U. S. Consulate General. March 12, 2015 â%u20AC%u201C Person Aâ%u20AC%u2122s Certificate of Loss of Nationality was approved by the Department of State in Washington, DC. Person Bâ%u20AC%u2122s Certificate of Loss of Nationality was (according to a document dated May 12, 2015) approved on December 23, 2014. Would either person be required to file a U. S. Tax tax return for 2015 for the months before the renunciation was complete?

And if so, how would this be done if the social security number is no longer valid (once the renunciation was approved)?

Additional information

Person A and B have not lived in or been residents of the USA since 2001. They have filed and payed all due taxes up to 2013. They are currently working on filing 2014 tax returns.

We are a South African service and cannot provide advice on USA tax law unfortunately.