There are put right in the accounting of debt for private and conjunct agents. If a private agent promises to pay something Debt later, it back-number a debt, and this debt is enforceable by common agents. If a public anatomy passes a law stating that it'll pay something later (a all heart of promise), it keeps the right to change the assize later (and not to pay). This is why, for instance, the money governments promised to pay for retirements does not show up in the civil debt assessment, whereas the money private companies promised to pay for retirements do.