You've probably received letters and emails and Web hectorings from businesses (credit cards, utilities, banks, investment companies) offering to stop sending you printed paper statements and send you email statements instead. The real reason is that this saves a lot of money for the business. But it has to be sold to the consumer, who feels much more security in printed paper trails than in ephemeral emails.
This from an electric utility:
"As we strive to provide you with the best customer service, we wanted you to know that you have the option to receive your bill online. Paperless Billing is a great alternative way to get your bill, providing convenience and peace of mind." Et cetera.
But the kicker is in the "Two Easy Ways to Sign Up" box. The letter says, "Online, Visit xxx.xxx.com/paperlessbill." That's okay, but then there is a highlighted, yellow box with "Promo Code: QKN3X" in it.
Wait a minute. Aren't promo codes used to get a discount or extra benefit? How can you have a promo code for signing up for paperless billing? If you don't have the code, will they refuse to sign you up? My guess is that the "promo code" is probably your encrypted account number, but why cast it in terms of a promotional benefit?