This is one of the questions about his duties to file to complete his renunciation of his US citizenship

Question:

I renounced my US citizenship on January 17, 2019.  Since moving to Europe in 2010, I have been filing my tax return online each year and have e-mail confirmations of acceptance, as well as automatic messages that my FBAR forms have been received.

With regard to form 8854, there is no section for having expatriated in January 2019. How soon after my renunciation date, should I submit the form?  Since my citizenship terminated on January 17, is it necessary for me to file either a tax return (form 1040) or FBAR next year for this 17-day period in 2019?

In order to renounce you will need to have the last five years of taxes filed, and then also file Form 8854 with your final tax return.

You will also have to be up to date on your FBAR filings (needed if you have more than 10K in foreign accounts).  The final exit from the US is declared with Form 8854 and a dual status return.

If you renounced in January 2019, your final exit from the US will be filed in 2020 when the 2019 tax forms are released. The dual status return will cover the period up until you renounce (on the 1040) and also the period after you renounced (on the 1040NR portion).

I hope this helps!