Eu settlement scheme

My daughter who is 3 year old, she got indefinite leave to remain, we can check on line, but for her application we dis not reciveid any email containing her unique application number. For other two daughter I reciveid email containing application reference number.
Now, I am applying for British citizenship for kids, and on application it asking me for eu settlement scheme reference number.
Plz guide me and what documents I need for three kids under 10, applying for British passport, along with their mother... all French citizens.
Many thanks.

You might try to contact the EUSS resolution centre at 0300 123 7379 though the lines are always very busy. Another thing you might try is a Subject Access Request with the Home Office (specifying you need the UAN for your daughter) https://www.gov.uk/government/publicati ... mmigration

If you can't retrieve it, explain in the cover letter that you don't know her UAN and what efforts you made to retrieve it.