Members of staff that are employed via an agency need to be recorded on the Additional Headcount section of the export. No information is required regarding their employment.
The government guidance advises the below in regards to agency staff members:
'Service agreement records are required for agency teachers in regular service, including those supplied by a local authority acting like a supply agency. They are not required for support staff, including teaching assistants. Support staff employed via a third party and in school on census day are collected in the third party headcount. If schools record such staff and return workforce level data on them in SWC, the DfE will be happy to receive it. However, there is no requirement to do so.'