Emma has spent her whole life thinking she was a British citizen.
Born in the UK to a Portuguese mother, she has only ever lived here and has a British birth certificate.
So it came as a huge surprise when the 22-year-old's request for a British passport was rejected.
Following Brexit, EU citizens living in the UK were offered the chance to apply for settled status.
Last year, however, Emma realised she had missed the deadline to apply.
She understood she was not officially a British citizen when she applied to be a care worker and needed to show the right to work.
She is not allowed to appeal the Home Office's decision and risks being removed to a country she has never lived in.
"When I got the rejection letter I was basically told how to leave the country," she said, adding that she was "shocked".
"There's a high chance I could be deported to Portugal and I would be separated from my family," Emma (not her real name) said.
"I would have to start a whole new life."
Emma's mother applied for settled status successfully and can remain in the UK permanently.
Emma has been told she can resubmit her application with additional evidence showing she meets reasonable grounds for applying late. She is doing this, but in the meantime can't work, open a bank account, rent a flat or get secondary care on the NHS.
The deadline for most people to apply for settled status was 30 June 2021, but applications are still considered past that deadline.
In August 2023, however, the Home Office tightened the criteria over "reasonable grounds" for late applicants.
Between July 2022 and June 2023 an average of 1,730 applications a month were found to be invalid, but in August 2023 that figure jumped to 9,470 and in September - the latest month of official data - it rose again, to 13,930.
Emma's situation is also being encountered by other European citizens in the UK.
Dumitru Calota, a bus driver and Romanian national who has been working in the UK since 2016, was told his application for settled status could be refused on grounds of "false documentation".
Mr Calota has pre-settled status - permission to remain in the country for five years - which in his case expires in 2025. He has been trying to obtain settled status.
He submitted his HSBC bank statements as proof of residency but was told by the Home Office that his statements were "false documentation" and therefore they are considering refusing his application.
"I was treated like a criminal," he said. "I didn't expect an official document to be considered false by the Home Office."
Luke Piper, head of immigration at the Work Rights Centre charity, is concerned that the rise in invalid applications will create a whole new cohort of vulnerable people who might be exploited because they don't have settled status.
"We're going to have a long-standing population of people who are undocumented in the UK and they will become more and more entrenched into their being undocumented, not able to work, not able to rent and being exposed to potential exploitation," he said.
"I've come across cases where people who haven't applied to the settlement scheme are being exploited by bad employers and people smugglers."
A Home Office spokesperson said: "More than two years have passed since the deadline for applying to the scheme, which was widely publicised. We continue to accept and consider late applications from those with reasonable grounds for their delay in applying.
"The EU Settlement Scheme has provided millions of EU citizens and their eligible family members with the immigration status they need to continue living and working in the UK now that we have left the EU."