How can you cancel a trade or purchase request?

Some times you start a trade or purchase request and then for one reason or another, you need to cancel it. How can that be done?

Simple really. Open the conversation you want to cancel. Just below the puzzle picture box there should be a button that lets you close the conversation. This will cancel the request and close the conversation.

If you close it by accident, you have a few days to re-open it.

Be aware, if you or the other party has already shipped a puzzle, the conversation can no longer be closed without completing the transaction.