The way the Government designed the EUSS means that EU citizens and non-EU family members (EEA+ citizens) who missed the deadline automatically fell out of status and rights and became undocumented migrants overnight.  
Estimations suggest this could be tens or even hundreds of thousands of people. 
We know that it is the most marginalised – older and disabled people, looked-after children, Roma communities and survivors of domestic abuse – who are the most likely to have slipped through the cracks. 
These EEA+ citizens are now subject to a series of policies commonly called the Hostile Environment, which criminalise work, bar them from accessing free healthcare and the public safety net and make it illegal to rent a home, access homelessness assistance, open a bank account or obtain a driver’s license.