Deferred Interest

I had a purchase with 30 months of deferred interest. If I paid off balance within the 30 months, the interest was not to be collected. I missed the payoff by 5 days due to an oversight on my part.

  • Is the full amount of deferred interest payable or should/can it be prorated?
  • If I don’t pay, can they charge interest on interest?
  • Can they charge late fees?

tx, frank