Memo codes

#Format

Every checkout gets its own memo code, shown as XN-7F3K-Q9S: the prefix XN, six random characters and one check character. It is unique across all orders.

• The characters come from a 31-symbol alphabet without 0, O, 1, I and L, so nothing can be misread.
• Upper or lower case, dashes and spaces don’t matter. Other words in the note don’t matter either.
• Forgot the “XN”? The seven characters alone are recognised too.

#The checksum

The last character is calculated from the others. Any single wrong character, and any two neighbouring characters swapped, produce an invalid code — so a typo can never match someone else’s order by accident.

#Typos and missing memos

An invalid or missing memo isn’t a problem in most cases: the payment is then matched on the two other keys, your X handle and the exact amount. If those don’t identify one order either, the payment goes to the creator’s review queue. See payment matching.

#Unique amounts

If you already have an unpaid order with the same creator at the same price, your new order costs one cent more ($8.01 instead of $8.00), the next one two cents more, and so on. That way the amount alone tells your orders apart, even without a memo. Always send the exact amount shown.