This all sounds very technical but I think I'd rather have paid my mortgage than be on tenter hooks for the last 19 years hoping the bank doesn't remember my existense! I'm also feeling somewhat ambivalent about this: on the one hand, given the way the banks have shafted us for heaven knows how long, I'd say good luck to you if you get away with it, on the other hand it also sounds rather dishonest - you know you still owe them the money, you should acknowledge the omission exists (which was your's as well - you have a duty to pay your debts) so morally you should pay up. If you intend to negotiate with the bank, go for today's interest rates, I think you'd get a shock it you looked back to what they were 19 years ago.