Travelling as a UK-EU dual citizen

Recently, I finally became a German citizen after just about 12 years living here, making me the holder of two passports. Not directly career-related, but possibly the biggest achievement of my life so far, given everything that has gone into it, even before I moved to Germany.

However, it does also mean I have to use my head more when passing in and out of the Schengen Area (which in most cases overlaps with EU, so for the purposes of this post I will use them more or less interchangeably).

So, here's a little guide.

I always assumed the rule of thumb was to use the passport of whoever's soil you're currently on. After all, in the UK I'm legally British, in Germany I'm legally German (this requires a bit of a mental adjustment, as I've spent years feeling too German for the UK and too British for Germany).

And while this is true, in practice, it is not the entire truth. A more accurate statement is: you cannot enter or leave the respective country on the other's passport. When you check in online and are asked for your passport details, you should put the ones of the destination country, not the one you're currently standing in. Otherwise this may raise questions about whether you have the unconditional right to travel there, regardless of where you are actually resident.

Germany to UK 🇩🇪🛫🇬🇧

Since 2025, getting an ETA has been mandatory for all EU nationals travelling to the UK. If I were to put in my German passport details for a flight to the UK, the system doesn't know I'm also British and therefore don't need an ETA — or rather, it has no reason to assume this. Thus, I should put in my UK details.

If you're checking in luggage and are asked for your passport at the counter, it should be the same one you used for your booking to avoid mishaps.

Before leaving the Schengen Area, there is always an exit control, and you should show your EU passport there if you have one. This one is easy for me to remember, as years ago, I naively just showed the photo page of my UK passport, assuming they could see my status on the screen. The officer asked how long I'd stayed in Germany and I was like, uhhh I live here. He raised an eyebrow at me, flipped to the page containing my residence permit and, switching to German, sternly told me I should show that page right away next time. So you see, even with one passport, it's not always obvious.

Anyway, when I became a German citizen, my residence permit became void/redundant. The status I'd held vanished, and so from a German perspective, as long as I am using my UK passport, I am a stranger. Without a German passport, the system would look for proof that I hadn't overstayed in the EU or anything. So, German passport when leaving Germany.

Once you land in the UK, use your UK passport at the border control gate.

UK to Germany 🇬🇧🛬🇩🇪

I checked in online using my German passport details for the first time! Felt strange and exciting.

For this leg of my trip, I actually didn't have to get out my UK passport once. The airports there, or at least the ones I've used, don't have exit controls, so I didn't have to do anything. While there was an informal ID check against my boarding pass (I used the German one, as it matched my booking details), nothing needs to be officially scanned and registered in a system.

Entering Germany/EU, obviously scan German passport at the border control gate!