Far riskier than it sounds — if the balance isn’t paid in full by the deadline, interest is charged retroactively on the entire original purchase amount from day one.
How it works
If the balance isn’t paid in full by the deadline, the purchase amount times the deferred APR, times the promo period as a fraction of a year, gives the retroactive interest charged. Paying in full avoids this entirely.
What this does not include
This computes the retroactive interest on the original purchase — it doesn’t include any interest that would also accrue going forward on whatever balance remains unpaid after the deadline passes.
How to use this calculator
- Enter the purchase amount, deferred APR, promotional period, and whether it was paid in full by the deadline.
Frequently asked questions
Why is this called a “trap” for consumers?
Many cardholders assume it works like standard 0% APR (interest simply starts accruing going forward if unpaid) — the retroactive nature, charging interest back to the original purchase date, often surprises people who miss the deadline by even a small amount.
Does paying the minimum payment avoid retroactive interest?
No — only paying the *entire* balance in full by the deadline avoids retroactive interest; paying the minimum each month still leaves the account exposed if any balance remains at the deadline.
Are deferred interest promotions common?
Yes — particularly on store-branded credit cards for larger purchases (furniture, electronics, appliances), often advertised prominently at checkout.
