Dunning is the structured process of contacting customers who haven’t paid by the due date to request payment. The word comes from the 17th-century English verb dun — “to make persistent demands.” In modern small-business and B2B contexts, dunning is the cadence of reminders, follow-ups, and escalations that takes an overdue invoice from “we sent it and they forgot” to “this is going to collections.”

What it means in practice

A typical B2B dunning sequence on a Net 30 invoice runs in stages:

StageDayActionTone
130Polite reminder emailNeutral — “just checking”
237Follow-up emailFirmer — references first reminder
350Phone or DMPersonal — voice, not email
460Final notice email + late feeFormal — explicit consequence
575Demand letterLegal — registered mail
690Escalation to collections/factoring/legalOut of your hands

The specific spacing isn’t sacred — adjust by ±5 days based on industry norms. What matters is the shape: never two reminders in the same week, never more than 14 days of silence past day 30, and a clear escalation ladder so each stage has a believable next step.

A complete walkthrough of the templates and tone for each stage is in how to recover unpaid invoices without sounding desperate.

Why it matters for invoice reconciliation

Dunning only works if your unpaid-invoice list is accurate. The single worst outcome of B2B collections is sending a dunning email to a client who already paid you — they read it, get offended, and you lose the relationship over a bookkeeping error. The frequency of this mistake is higher than most operators admit; in tight informal surveys, roughly 1 in 8 dunning emails go to clients who have already paid.

The fix is a reliable reconciliation step before the dunning step. The order:

  1. Pull bank statement CSV
  2. Pull invoice list CSV
  3. Run a bank reconciliation to confirm which invoices are actually unpaid
  4. Send dunning emails only on the verified unpaid list

checkunpaidinvoices.com automates step 3. Drop both CSVs, get a four-bucket result (Paid / Likely paid / Unpaid / Anomalies) in 30 seconds. The “Unpaid” bucket is your dunning list.

Dunning automation

For businesses with high enough invoice volume, the dunning cadence becomes worth automating. Tools in the space:

These tools watch your accounting system, identify overdue invoices, and send the reminder emails on schedule using templates you write. The reminders look like they came from you personally. Most charge $50-200/month for small business plans.

The reason to automate isn’t typing speed — it’s consistency. The hard part of dunning isn’t writing one polite email; it’s writing the second one seven days later when you’d rather avoid the awkward conversation. Automation removes the avoidance.

Affiliate note: if your dunning identifies a cluster of clients consistently 60+ days late, factoring services like Bibby, Fundbox, or Resolve can buy those receivables at 70-95% of face value. See when an invoice becomes bad debt.

Hard vs. soft dunning

A useful split:

Most B2B businesses never move past soft dunning with most clients — the reminders work, the client pays, the relationship continues. Hard dunning is for the 5-10% of cases where the client either can’t or won’t pay.

Cultural differences

Dunning norms vary by region:

If you sell internationally, adjust the tone and cadence by client region. The 90-day cliff is universal; the language to navigate it is not.

Before you send a dunning email, make sure the invoice is truly unpaid. The reconciliation tool flags it from two CSVs in 30 seconds — no signup.

Quick FAQ

When does dunning legally cross into harassment? Most jurisdictions require dunning to stop after a reasonable number of contacts (typically 3-5) and during specific hours (typically 8am-9pm local time). After referral to collections, the collections agency takes over and is subject to its own consumer-protection laws — in the US, the FDCPA.

Can I charge interest on overdue invoices? Only if your contract or invoice terms specified the rate at the time of issuance. Adding interest retroactively after the invoice is late is legally unenforceable in most jurisdictions, though it may still motivate payment behaviorally.

What’s the difference between dunning and collections? Dunning is what you do internally before referring out. Collections is what a third-party agency does after referral. Dunning ends when the client pays, or when you give up and send the case to collections.

Should I publish a public list of bad payers? No — never. Even in jurisdictions where it’s legal, the reputational damage to you exceeds the damage to the deadbeat client. There’s no upside.