Which passport to travel on?

[moira123io]

DD is a UK/NZ dual citizen. She is leaving London to visit family in the US for a month, then will be flying to NZ where she plans to live.

She was in the US last year on her UK passport so has a valid ESTA. However since her final destination is NZ, and she won't have a return ticket to show customs, should she travel on her NZ passport for the whole trip?

She should use the British as it has the valid ESTA. She needs to have proof of booked onwards travel to NZ in her hand luggage as when she enters the US the border official may ask for it. And she probably won’t be able to check in online for her flight to the US if it’s booked as a one-way, she’ll be fine at the desk though.

Actually... not having proof of her leaving the US on her British passport might cause a problem (not at the time but further down the line if she goes to the US again) if she will use her NZ passport for the flight from the US to NZ... so if that’s her plan then ignore what I said above (except for the bit about no online check in and proof of onward travel being required) as I’m not an immigration lawyer. Hopefully someone more learned will be along with better knowledge!

You can use the NZ passport to enter NZ only. Or just the U.K. passport for the whole trip. Is she going there for a long trip that will be longer than the allowed stay for British passport holders? DH did it once entering NZ with a British passport. They only told him he should remember his NZ one at custom and let him through. I have three citizenships and only ever use one at a time. Too expensive to renew those damn things.

She should enter and leave the US on her UK passport and then switch to her NZ passport mid flight (so to speak) and enter NZ on her NZ passport

Can't use the Esta without the corresponding passport. Wherever you travel your ticket must match the passport you booked it on. No idea if NZ has some sort of Advanced Passenger info kind of thing where the airline has to tell them who's coming before they land. This will be matched to your passport.

I have dual nationality US/Italy. When I travel I leave the US with my US passport and then as someone else described, switch mid-flight and enter the EU with my Italian Passport. When I leave the EU I leave with my US passport and arrive in the USA with my US passport.

Sofia - but you don't need an EStA.

Correct, but the concept is the same. The OP's DD would leave the UK and enter the US on her UK passport. The US doesn't need a "return" ticket, just a ticket to show that OP's DD is leaving the US in a finite amount of time. She would then leave the US with her UK passport and arrive in NZ with her NZ passport. The only hitch would be if someone from the UK needs a visa to visit NZ, which I don't believe is the case.

Enter US with the UK passport
Leave US with UK passport
Enter NZ with NZ passport

Call Immigration NZ and check out with them about arriving with a British passport and not leaving after the allowed six months because she is a NZ citizen too. It can’t be unusual and they have always been happy to answer questions for me.

Immigration NZ