In SAGE Payment Solutions’ virtual terminal, transactions have a memo field. However, the gateway’s HTTPS Bankcard Specifications API documentation doesn’t mention a way to programmatically set this field. Using the HTTPS POST API, is there a way to pass in memo text?
Yes! In your authorization request, put the memo text in a field called T_memo.
Thanks to Cornerstone, one of my client’s credit card processing vendor, for passing on this tip!

Nice tip – thanks! Do you know if Sage Payment Solutions offers an interface for POSTing data directly from the client and then redirecting back to your site?
I don’t. You might try asking your Sage Payment retailer.