Consumer purchases can be 27 times more expensive when paid one month behind schedule on deferred interest cards, according to a study done by CardHub.

These cards, offered by 82.2 percent of major retailers, catch consumers with their transparent policies. The average household has $6,700 in credit card debt, which is added to by these transparent options.

"We all know that too few people truly read the fine print of financial agreements, which means most folks don’t find out that they signed up for deferred interest until their costs are suddenly inflated," said Odysseas Papadimitriou, the CEO of CardHub, in a statement.

This financing option is similar to a 0-percent introductory rate credit card, but it has a major difference. When a balance is not completely paid off on a deferred interest card, the interest is applied to the entire original balance, instead of only the remaining balance.

Of the retailers that offer financing, 37.8 percent offer a deferred interest plan, and are not transparent in their policies. Papadimitriou urges consumers to look out for these hidden costs.