Only some census items used
The guide to the school census published by the DfE marks the census items that are used to determine your school's funding allocations by including ‘[used for funding]’ in the section title.
The marker is there to let you know that those data items need to be especially accurate, because errors with these items can affect how much funding you receive.
Funding for pupils of statutory school age and post-16 pupils is allocated based on autumn census returns.
For children in the EYFS, funding is based on returns from the spring census.
This is explained in section 3 of