Dunning is the follow-up process for money owed: the escalating sequence of reminders that starts before or at the due date and continues, with increasing firmness, until the payment arrives or the matter escalates. In rental operations a typical sequence runs from a friendly upcoming-rent reminder, to a due-date notice, to past-due messages, to whatever formal step the lease and local law provide. The term comes from software billing, where automated dunning — including retrying failed payments — is standard practice.
Good dunning is consistent, polite, and boring: the same sequence for every tenant, every month, with a clear record of what was sent and when. That consistency is also protection, since ad-hoc collection pressure applied unevenly invites fair-housing and harassment problems, and communications about debts are regulated in some contexts — especially once third-party collectors are involved. Automation helps precisely because it never forgets, never gets angry, and leaves a clean trail; the formal legal steps that may follow a failed sequence remain decisions for a human, informed by local law.
This is general educational information, not legal or tax advice. Rules vary by state and locality and change over time — check your local law and confirm specifics with a qualified professional.