I asked my legal friend and she said that to claim estoppel you would need to have had something in writing. For example, if a lender said they'd take a small lump sum in full and final settlement, you paid up and they came back several years later for more, then you could claim estoppel. Its basically where you've paid money under the assumption that it would be the end of the matter. If the creditor comes back saying it isn't and you've got it in writing that it was settled, then you can claim estoppel.(posted 8547 days ago)Pendle