“No interest if paid in full within 12 months” is a deferred-interest offer. Interest accrues from the purchase date at the standard rate. If the balance is cleared in time, the interest is never charged. If any balance remains, all of the accrued interest is added at once.
This differs from a true 0% APR installment plan, where no interest accrues during the term. The US Consumer Financial Protection Bureau reported that consumers paid $1 billion in deferred interest on medical credit cards and loans from 2018 to 2020.
From our data: We track 14 patient financing providers and record the type of credit check and promotional terms for each.