We have updated the guideline Assessing the Terms of an Access Application. This guideline was written to bring existing principles together to provide convenient guidance for agencies dealing with applications where the documents sought by an applicant cannot be identified.
It is essential to remember the importance of working with applicants in these circumstances, that scope should not be interpreted technically, and that searching for and considering documents potentially responsive to an application will always require a degree of investigation and analysis.
The applicant themself can be one of your most valuable tools. Talking to them about what information they're looking for can, in many cases, be the fastest way to sort things out. Most applicants don't know how agency recordkeeping systems work or, if they do, may not know how your agency's works—and as the guideline notes, what's compliant for one agency may not be compliant for another.
Obviously, a conversation won't always be possible, but where it is, you can save yourself a great deal of work, make life easier for yourself and the applicant, and work together to scope out a way forward.
See the updated guideline here: Assessing the Terms of an Access Application