Revolut is warning customers of possible changes
Virtual bank app Revolut has written to millions of customers across Europe.
They are asking them to upload new ID documents in case there's a hard Brexit.
The firm was started back in 2015, with a view that money should be borderless.
But the startup said this morning it feared being blocked from trading operating if there's no deal.
"We know this is a pain," it told customers, telling them they'd have to take another selfie - and dig out their passports.
In an e-mail to customers, it has asked them to upload new ID documents.
It said: "Right now, all of our customers in Europe are tied to our UK Electronic Money License, which we have passported across the European Economic Area."
"If a no deal outcome were to happen, we would no longer be able to passport this licence across Europe."