If you were not charged a late fee, it is unlikely they can retroactively charge it. Whan you need to be careful of is being sure the late fee wasn't charged and you didn't realize it. You need to get an accounting of your mortgage loan...you can request the payment history. Typically the mortgage company will charge the late fee and apply part of what you paid for the next month to that fee. It is very unusual for a mortgage servicer to not charge the late fees as this is mainly how they make a lot of their money in this new complicated mortgage securitization world we live in.
