Field display only if completed

Hi,

I don't see any "PEC" field on your registration ?
monosnap.com/file/DZnsKcfsyTXct9Dkhv1pYX2BL4zTRy
Anyways, in the settings of that custom field, you have a "display limited to" that you can use to only display a field for one value of another field.
So what I would recommend is to create first a custom field "type" where the customer can choose "individual" or "company" and then use the "display limited to" setting of the "company" field and the "PEC" field to only display when that "type" field is set to "company" and activate the "required" setting of the "company" field.
That way, when "company" is selected, the company field will have to be filled and thus you'll be sure that the customer can only use the PEC field if the company field is also filled.