# Validate Document On Save
`Be.Smart T4I -> Be.Smart T4I -> Advanced settings -> Auto iProperties -> Validate Document On Save`
On invoking the Save command, a check can be performed whether the document being saved conforms to preset rules. The activation of the individual validation checks can be set in Advanced settings.
On Save document validation settings
If at least one of the validation checks fails, the save process is terminated, and the issue description is listed in a dialog box.
Example of the On Save validation error message
## Virtual Components in Assembly
The assembly must not contain virtual components. If they are present, the save command is canceled.
Virtual component in the assembly
## Invalid Units of Measurement
If there is a problem with units in BOM, the assembly cannot be saved.
## Whitespace Before or After the Part Number
The iProperty *Part number* must not start or end with spaces, otherwise, the document cannot be saved. This rule applies not only to assemblies but also to parts.
