The sponsor's passport provided with the application MUST be current and valid. If the sponsor does not have a valid, current passport, they cannot use an expired one and instead must provide a number of other documents to prove their UK citizenship, and their ordinary residence in the UK for the last 3 years.
So, the easiest option will be to apply for a new passport for them ASAP and scan every single page of it.
If they do not have a new passport by the time you apply for ILR, they will need to provide the following documents instead:
- full birth certificate (showing their parents’ names)
and
- at least one other formal document as evidence of ordinary residence in the UK for the last three years.
and
- If they were born on or after 1st January 1983, they must also provide both their parents' birth certificates as well, to prove they were born a UK citizen.
Suitable formal documents showing ordinary residence include:
- notice of income tax coding
- driving licence
- building society savings book(s) /bank statements
- National Insurance or National Health Service registration issued by the Department for Work and Pensions or a local health authority