The reason that this is happening is likely the way that the identification type is setup on your system.
Amend system settings
This can be amended by following the steps below:
Click Settings via Admin or Configuration, this will depend on how your system is configured.
Search for Work Eligibility/Identification and click into it.
Search for the identification type then set the Document Entry to Birth certificate.
Still requiring passport or visa expirations
If you have amended this and you still get asked for passport or visa expirations, follow the below steps:
Click Settings via Admin or Configuration, this will depend on how your system is configured.
Search for Work Eligibility/Identification and click into it.
Search for A document giving the persons permanent National Insurance number and name.
This could be a p45, p60, NI card, or a letter from a government agency or search just Document, this will be the first option.
Amend the document entry to be set to Birth certificate.
Click Save.