People who expatriate often assume that they must handle their tax filings immediately after their expatriation date. Not so. The final year’s tax filings are done in the following year.

On Form 8854 you are supposed to tell the IRS when you renounced citizenship or abandoned your green card.
When someone expatriates (renounces U.S. citizenship or abandons a green card after holding it for a long time), there is one eternal truth:

You still have to file a U.S. income tax return for the final year that you were a citizen or a green card holder, even if it is only for part of the year. This is usually (but not always) a dual-status tax return. See IRS Publication 519, Chapter 6.

The Form 8854 is filed along with that final tax return. From the Instructions to the 2013 Form 8854, at page 3, in the right hand column:

When To File
If you expatriated after June 16, 2008, attach Form 8854 to your income tax return (Form 1040 or Form 1040NR) for the year that includes your expatriation date, and file your return by the due date of your tax return (including extensions). Also send a copy of your Form 8854 to the address in Where To File, later. If you are not required to file Form 1040NR or Form 1040, send your Form 8854 to the address in Where To File, later, by the date your Form 1040NR (or Form 1040) would have been due (including extensions) if you had been required to file. (See Resident Alien or Nonresident Alien in the Instructions for Form 1040NR.)

For someone who expatriates in 2014, that final tax return will be due in 2015. The filing deadline will either be April 15, 2015 or June 15, 2015, depending on circumstances. An extension request can be made, giving you until October 15, 2015. A further extension request is possible to December 15, 2015.
If you are a covered expatriate and you have deferred compensation plans (think “pension”), you must file Form W-8CE with the compensation plan administrator within 30 days of your expatriation Date.
If you do this, your U.S. income tax on pension distributions will be 30%, as the payments are made to you. If you miss the 30 day deadline, you are treated as if you received a giant lump sum distribution of your entire lifetime’s worth of pension payments. This will create a Godzilla-sized income tax payment that the IRS will be keenly interested in receiving promptly.
The problem is a cash flow problem. If you are receiving small payments every month for the rest of your life, you probably don’t have the cash available to pay some hundreds of thousands of dollars in income tax today.
 http://hodgen.com/blog/page/2/