I don't understand how the listing on your AmEx card has anything to do with using the voucher. AFAIK the voucher must be booked on delta.com and your corporate travel must be booked through their agency. Are you hoping to just show your employer the credit car statement and tell them that it was booked through the agency? BTW, if it's personal travel, even if it originates at the client site, why is the employer involved at all in this transaction? Or does policy say that you may travel to a different location instead of home on weekends/holidays and have the company pay?