You can manually enter one into one of the Additional Info fields and rename the field appropriately but to be honest, it doesn't get you further ahead.

I have always ignored it as it is optional governmental forms.

Richard is right that it doesn't get you any further ahead, however, I set up an employee number in the additional info fields and then I use this alpha/numeric number in payroll, ROE's and benefits.  We scan everything so when I want to link and/or search for documents I use that unique number to find all documents.  With our System I use as for example for Joe Block, his number would be BLOJ001. 

Richard is right that it doesn't get you any further ahead, however I set up an employee number in the Additional Info Fields and then I use an alpha/numeric number in Payroll, ROE's, TD Forms and Benefits.  We scan everything so when I want to link and/or search for documents I use that unique number to find all documents.  With our System I use as an example: for Joe Block - his number would be BLOJ001.  I also use the Additional Info Fields to record Driver's Licence numbers and Alberta Health Care Numbers. 

Thanks Marj, this is good to know!