We just caught this on an interest free loan from Home Depot. We bought a bunch of stuff for the house including some big ticket items for the remodel job underway. By signing up for a credit account we got a 10% discount which was significant. Also, being that it was interest free for one year, we decided to let it float and take care of some other issues with the money. Now this is all fine, but luckily this came to my attention in the fine print; and really by chance, it was easy to miss: If the loan is not paid in full at the one year mark, a high rate of interest - I think ~21% - is applied retroactively to the entire year!!!