dependant on your version it is available. In the older versions, this field is provided but hidden. You would need to move/hide another field (usually Nickname is a good one) and put the Corporate ID in its place .....
I'm facing a strange behaviour using Corporate ID when searching:
If you use the advanced search query bar and searches for "Corporate ID" = "XXX", the result is not the same than entering a Corporate ID, clicking ENTER (that will populate Customer's Info fields) and clicking Search after this.
I'm trying to find out why results are different.
If you have made a field visible then you need to take care fo the workflows which sets the temporary fields on Help Desk form.
Take the logs while hitting enter in Corporate ID field, you will get an idea what is happening behind the screen.
There is an AL Guide called after you hit enter in search field.