This Help Article covers;
An example is a Staff Member purchasing tools and booking them to a Job
To Remove a Job Reference
Quick flow:
Purchase Invoice/Credit Note
[REASSIGN]
Hover over the "Job" field [X]
[REASSIGN]
1. From an Open Purchase Invoice/Credit Note Window, Press the [REASSIGN] button to display the Reassign popup
2. From the Reassign popup, Hover over the Job field to expose the [X], then Press to clear the field, then Press [REASSIGN] to save the cleared Job Reference