I need to have a reference number (rn) or purchase order (po) as an optional field during the credit card part of the checkout. I am using Authorize.net for credit cards and there isn't an out-of-the-box solution to include an rn or po with the information.
For those that aren't familiar with rn or po, it's an internal number that the customer provides for purchasing reasons (most commonly if the customer is a business). They'll see the rn or po on all the invoices, transactions, packing slips and receipts.
There is little to no information on integrating purchase order numbers or reference numbers with Authorize.net and It's something we need on our checkout to ensure customers are able to track their purchases internally.