thanks guys.
it appears to be a problem with the relationships and not regarding the splitting.
It's probably my lack of understanding (as always)
Do all tables in a query have to have 'some' info in them?
Basically my query isn't returning any results but when I remove a table it does.
The table I removed from the query doesn't have any data in it for the current record (it's to be entered after the query has run). The query looks at one table and if a yes/no field is True and the first table's yes/no field is False return the records.