Bar Coding

I hope this is the right place to ask this...

We would like to print a bar code for every invoice that we receive (to pay)
for tracking purposes. I am not sure where to even start to do something
like this. I want to find out the most common practices so I can figure out
the best solution for us. I have one example, but that requires some sort of
chip on the printer for this to work. We would like to try to do this
without that chip if possible. If anyone could give me some sort of
direction, that would be great! 

Thanks,

Mike Wills
Taylor Corporation
Lawson Administrator/Programmer
AIM: iSeriesCodePoet