An account needs to be 90 days in arrears before you can verify a debt, and begin to move enforcement. For a complete commercial process, three bills are sent out – instead of just one – and are sent a minimum of 30 days apart.
The amount of the bills, which is based on a daily amount, stays the same because that specific amount must be at least 90 days in arrears. So even though the fees continue to accrue until the situation is corrected, the 2nd and 3rd bills stay the same in amount.
An example of this process of multiple bills leading to escalation, is how, when someone has a credit card amount owing (without payment) that is 90+ days past due, the credit card company generally escalates and moves toward enforcement. It’s the same thing with a mortgage. In commerce, all of the mechanisms for enforcement – e.g. collection agents, liens, seizures, repossessions, etc. – are available at 90 days, but not before.