Sailing Permit malarkey

Hi, all-

I am trying to figure out all we need to do before leaving the US to re-locate permanently to the UK, and I keep stumbling across new things everyday. The latest: the Departing Alien Clearance (Sailing Permit). My question is whether we need to fill this out at all, and whether we need to do it before we go.

I am a dual citizen, my husband is a UK citizen here on a green card. We have filed US income taxes jointly every year and will be doing so soon for 2015. We will both be working until March, though, so understand we will also need to file jointly for 2016. We know we need to inform the UCIS about our change in address, and thought we'd need to inform the IRS too, but do we need to do that with this Sailing Permit form? It looks complicated, asks questions I don't have answers for yet (like UK address...we're still living in the US and won't know our new flat address until we get there and find one.), and seems unduly harsh to make us do while we're still in the midst of figuring out our 2015 income taxes. So...much...paper...work...

Thanks, friends, for any help you can provide!

Sorry, I realized I should have provided a link for future reference/anyone not familiar with this form:

https://www.irs.gov/Individuals/International-Taxpayers/Departing-Alien-Clearance-(Sailing-Permit)

As your husband is on a green card you will naturally be thinking of US expatriation tax tied with either keeping the green card valid or abandoning it with an I-407.

There is almost no compliance with the sailing permit rules, but if the green card is important to you it may be prudent to be one of the brave few who file one.

Thanks for the reply, @guya! Does that mean we'd only need to do the Sailing Permit if we intend on keeping the green card valid? We were definitely leaning toward surrendering the green card, since we intend for the move to be permanent.

If I'm following the requirements correctly for surrendering the green card is it right then that we'd just need to complete the I-407, or are there other tax documents in addition to that one I might not have stumbled across yet? 

Thank you, thank you, thank you!