I like to tag with registry keys.
Create a batch file or ps script similar to:
@echo off
set today=%date:~4,2%/%date:~7,2%/%date:~10,4%
reg add "HKLM\Software\MSAudit" /v "Last Audit" /t REG_SZ /d %today% /f
That would create a reg key with the date that the batch file was run. Every machine successfully audited just run the file against it to tag it. Then create a registry scan for that value to report. This will also put a reference to the audit outside of just lansweeper so that it can be validated independent of a single platform.
Hope this helps.