The B2B Dunning Process: How to Build a Collections Sequence Customers Actually Respond To

Every finance team has a dunning process, whether or not they call it that. In many companies it consists of a credit controller remembering to chase the accounts they happen to think of, sending a version of the same email they sent last month, and escalating to the sales rep when it feels awkward to keep pushing.

That is a dunning process in the same way that a pile of receipts is a filing system.

A real dunning process is deliberate: defined trigger points, defined tone at each stage, defined channel, defined owner, and defined exit criteria. Getting it right is one of the highest-leverage things an AR team can do, because the timing and quality of follow-up — not the payment terms on the invoice — determine when most B2B customers actually pay.

This guide covers what dunning means, how to design a B2B dunning sequence, what each dunning letter should say, how to automate it, and the point at which email-based dunning stops working.

What Does “Dunning” Actually Mean?

The word comes from the 17th-century English verb to dun, meaning to make persistent demands for payment. In modern finance it refers to the systematic process of notifying customers of overdue invoices and requesting payment through a planned series of escalating communications.

Two terms are worth separating:

• A dunning letter (or dunning notice) is a single written communication demanding payment on a specific overdue invoice or set of invoices.
• A dunning process or dunning sequence is the full escalation ladder — the series of contacts, their timing, and the rules that govern movement between stages.

In subscription and B2C billing, “dunning” often refers specifically to failed-payment recovery: retrying a declined card and emailing the customer to update their payment method. In B2B, where invoices are issued on credit terms and paid by bank transfer, dunning means something broader — the entire structured collections communication process against an open receivable.

This guide addresses the B2B case.

Why Most B2B Dunning Processes Underperform

Before designing a sequence, it helps to understand the failure modes.

Uniform treatment of a non-uniform portfolio. The most common design flaw is a single sequence applied to every customer. A strategic account with a $400,000 balance and a procurement process requiring three approvals receives the same templated reminder as a customer owing $900. The first is insulted; the second is under-pursued.

Starting too late. Many sequences begin at 30 days past due. By then the invoice has been overdue for a full month, and in most cases the reason is mundane and fixable — it never reached the right approver, it was rejected in a portal, or the PO number was missing. A pre-due reminder catches these before they become collections problems at all.

Chasing invoices the customer never received. If invoices are delivered manually into customer portals or by email to a general inbox, a meaningful share never reach the person who approves them. Dunning an invoice that was never delivered produces a confused customer and no payment. The invoice delivery gap is a frequent, invisible root cause of aged receivables, and one of several handoffs examined in the order-to-cash process.

Escalating tone without escalating consequence. Sequences that get progressively angrier while nothing actually changes teach customers that the warnings are empty. Escalation has to mean something — a credit hold, a stop on new orders, a conversation with a more senior person.

No dispute off-ramp. If a customer is withholding payment because of a pricing error, the correct response is to resolve the dispute, not to send reminder four. Sequences without a dispute branch keep pursuing invoices that can never be paid in their current form.

Stopping at email. The deepest structural limit. Well-configured B2B email dunning plateaus at roughly 25–40% response rates. The remaining majority requires a phone call, which historically meant human collectors and a hard headcount ceiling.

Designing a B2B Dunning Sequence

A well-built sequence has four tiers. The timing below assumes Net 30 terms and should be shifted proportionally for longer terms.

Tier 1 — Pre-Due Reminder (7 days before due date)

Tone: purely informational, no collections framing.

Purpose: confirm the invoice was received, is approved, and is scheduled for payment. This single message resolves the largest category of lateness — invoices stuck in the customer’s approval workflow — before the due date passes. It also surfaces disputes early, when there is still time to issue a corrected invoice or a credit note without the invoice ever going overdue.

Teams that add only this step typically see a meaningful DSO improvement with no relationship cost whatsoever.

Tier 2 — Courtesy Notice (3–7 days past due)

Tone: assume good faith, assume an oversight.

Purpose: a light-touch nudge that includes the invoice number, amount, due date, a payment link, and a copy of the invoice attached. Most B2B lateness at this stage is administrative rather than intentional, and the message should reflect that. Critically, it should make paying easier — a customer routed to a self-service customer portal where they can view the invoice, download a statement, and pay immediately converts far better than one told to “please arrange payment.”

Tier 3 — Formal Dunning Letter (15–30 days past due)

Tone: firm, factual, unambiguous.

Purpose: a clear written demand that establishes a record. This is the message that matters if the account later goes to an agency or to legal, so it should be precise. It should state the specific invoices and amounts outstanding, the original due dates, the total balance, any contractual late fees or interest, a specific date by which payment is required, and the named consequence of non-payment.

Attaching a full statement of account at this stage is far more effective than listing invoices in the email body, because it gives the customer’s AP team a single reconcilable document rather than a claim they have to verify line by line.

Tier 4 — Escalation (45–60+ days past due)

Tone: consequence-driven.

Purpose: change the commercial relationship rather than send another message. Options include placing the account on credit hold, stopping new orders or shipments, escalating from AR to the account owner or commercial lead, involving senior finance on both sides, or referring to a collections agency.

The account should also be routed to a named internal owner with a task and a deadline. Escalation without assigned ownership is where aged balances go to die — everyone assumes someone else is handling it. A finance CRM with task management makes ownership explicit at this stage.

Segmenting the Sequence

The four tiers are the skeleton. Segmentation is what makes the process effective.

The long-tail segment is where automation pays for itself most obviously. These accounts are individually too small to justify a collector’s time, so in most organisations they receive no follow-up at all and quietly age into write-offs. Automated dunning makes pursuing them cost nothing.

What a Dunning Letter Should Contain

Regardless of tier, an effective dunning communication includes:

• Specific invoice references — invoice numbers, dates, and amounts, never just a total balance
• The original due date and days outstanding — establishing the factual record
• A single, obvious payment path — a payment link or portal login, not bank details buried in a footer
• The attached invoice or statement — removing any excuse related to non-receipt
• A named human contact — a real person and direct line, not accounts@
• A specific requested action and date — “payment by 30 September,” not “at your earliest convenience”
• An explicit dispute route — a clear instruction on what to do if something is wrong with the invoice

That last point is the one most often omitted, and it is the cheapest way to separate genuine slow-payers from customers sitting on an unresolved problem.

Automating the Dunning Process

Automated dunning software handles the mechanical layer: monitoring aging, triggering the right message at the right time, personalising content from invoice data, and logging every contact.

Trigger-based sequencing. Messages fire off invoice due dates and AR aging buckets rather than off a person remembering. Payment received mid-sequence halts the remaining steps automatically — which prevents the reputationally expensive mistake of chasing a customer who has already paid.

Accurate, real-time invoice state. A dunning system is only as good as its view of what is actually outstanding. If cash application is manual and remittances sit unmatched for days, automated reminders will go to customers whose payment is already in the bank. Automated cash application and reconciliation is a prerequisite for trustworthy dunning, not a separate project.

Personalisation from real data. Effective automated dunning pulls the specific invoices, amounts, PO references, and contact names into each message. Generic templated reminders are ignored precisely because they read as generic.

Full audit trail. Every reminder, response, promise-to-pay, and escalation logged against the account — which matters for credit decisions, for agency referral, and for any subsequent legal process.

Peakflo’s payment reminder automation handles this tier, including multi-entity and multi-currency sequences.

Where Email-Only Dunning Hits Its Ceiling

Here is the uncomfortable arithmetic. A well-designed, well-automated B2B email dunning sequence will resolve roughly 25–40% of overdue balances. The rest belongs to customers who read the email and do nothing, or who never see it because it lands in a shared inbox nobody owns.

For those accounts, the next effective contact is a phone call. Voice consistently outperforms every other collections channel because it is synchronous: the customer cannot defer the conversation, and the collector leaves with either a payment commitment or a stated reason for non-payment — both of which are more valuable than silence.

The constraint has always been capacity. A human collector manages 25–40 meaningful calls a day. At 2,000 overdue invoices a month, full phone coverage means a team of three to five people doing nothing else, which is why most organisations call only the largest accounts and let everything else age.

AI voice agents remove that constraint by conducting autonomous outbound collection calls at any volume — reaching the AP contact, referencing the specific overdue invoices, answering routine questions about amounts and delivery, capturing a promise to pay with a date, and writing the commitment back against the invoice. Engagement rates of 60–75% are comparable to human collectors, without the headcount ceiling. This is materially different from legacy IVR, which can only play recorded messages and route menus; the comparison is covered in AI voice agents vs traditional IVR for AR collections.

In a modern sequence, voice is not a replacement for the email tiers — it is inserted as an automated escalation step at Tier 3, applied across the entire portfolio rather than only the top accounts. For implementation detail, see how AI voice agents automate AR collections.

How to Build and Automate a B2B Dunning Process

Step 1: Segment the portfolio. Escalation speed, tone, and channel should differ by balance size, payment history, and strategic importance.

Step 2: Add a pre-due reminder. The highest-return, lowest-risk change available to most AR teams.

Step 3: Define four tiers with real consequences. Escalating tone without escalating consequence trains customers to ignore you.

Step 4: Route disputes out of the sequence. Disputed invoices need resolution, not reminder four.

Step 5: Automate the email tier on accurate data. Real-time cash application is what stops you chasing invoices that are already paid.

Step 6: Insert automated voice at escalation. This is the step that addresses the majority of balances email cannot reach.

Our Verdict: Dunning Fails on Consistency, Not on Wording

Teams redesigning a dunning process almost always begin with the message, rewriting templates in the belief that better wording will produce better results. Wording matters far less than timing, specificity, segmentation and follow-through. A plainly written reminder that arrives before the due date, references exact invoice numbers, and is followed by a call when it is ignored will outperform an elegantly drafted letter sent at day 45 with no escalation behind it.

The structural verdict is that dunning should be treated as a sequence with defined tiers, owners and consequences rather than as correspondence. Three design choices carry most of the weight: start before the due date so approval-workflow delays surface while they are still fixable, remove disputed invoices from the sequence entirely so reminders never chase money the customer cannot legitimately pay, and ensure escalation carries an actual commercial consequence rather than only a firmer tone.

Guidance from the Chartered Institute of Credit Management and the National Association of Credit Management consistently emphasises this structural framing over message craft, and in jurisdictions such as the UK the statutory position on late commercial payment and recovery costs gives the final escalation tier a legal foundation that many suppliers never invoke. Guidance from ACCA on credit control points the same way: process consistency, not persuasion, is what moves collection performance.

Conclusion

Dunning works when it is early, specific, segmented, consequential, and consistent — and when it reaches customers on a channel they actually respond to. Most teams have solved the email layer and mistaken that for solving collections. The balances that remain overdue are, almost by definition, the ones email does not reach.

Request a demo to see how Peakflo combines payment reminder automation with AI voice agents across the full accounts receivable lifecycle.

Frequently Asked Questions

What is dunning?

Dunning is the structured process of communicating with customers to collect payment on overdue invoices. It consists of a planned sequence of escalating contacts — reminders, formal notices, and escalation — each with defined timing, tone, and channel, designed to recover payment while preserving the customer relationship.

What is a dunning letter?

A dunning letter is a formal written demand for payment on specific overdue invoices. An effective one states the exact invoice numbers, amounts and original due dates, the total balance outstanding, any contractual late fees, a specific date by which payment is required, a named contact, and the consequence of continued non-payment.

How many dunning letters should you send before escalating?

Most effective B2B processes use three communications before commercial escalation: a pre-due reminder, a courtesy notice a few days past due, and a formal dunning letter at 15–30 days past due. Beyond three written notices, additional letters produce diminishing returns — the account needs a phone call or a real commercial consequence such as a credit hold.

What is the difference between dunning and collections?

Dunning refers specifically to the structured communication sequence that requests payment on overdue invoices. Collections is the broader function that includes dunning plus dispute resolution, payment plan negotiation, credit holds, agency referral, and legal action. Dunning is the first and largest stage of the collections process.

Can the dunning process be automated?

Yes. Dunning management software triggers sequences from invoice due dates and aging buckets, personalises each message with specific invoice data, halts sequences automatically when payment is received, and logs a full audit trail. Modern platforms extend automation beyond email to AI voice agent calls at the escalation tier.

Does automated dunning damage customer relationships?

Poorly designed automation does — generic templates, uniform aggression across all segments, and chasing invoices that are already paid or under dispute. Well-designed automation improves relationships, because messages are accurate, specific, correctly timed, and stop immediately when payment arrives or a dispute is raised.

How much can automated dunning reduce DSO?

Automating the email tier of dunning typically produces an 8–15 day DSO improvement for teams moving from ad-hoc manual follow-up. Adding automated voice outreach at the escalation tier commonly delivers a further 15–25 days by addressing the majority of balances that email alone never reaches.

When should a dunning sequence start?

The most effective sequences begin roughly seven days before the invoice falls due, with an informational reminder rather than a collections message. This catches invoices stuck in the customer’s approval workflow while there is still time to be paid on terms, and surfaces disputes early enough to issue a corrected invoice before the balance ever ages.

Should disputed invoices be included in a dunning sequence?

No. A disputed invoice is unresolved rather than simply late, and continuing to send payment reminders cannot produce payment while the underlying issue stands. Disputed and short-paid balances should be tagged and routed to a resolution workflow with a named owner, leaving only genuine slow payment in the collections sequence.

How do you segment customers within a dunning process?

Segment by balance size, payment history and strategic importance. High-value accounts with good history warrant slower, relationship-preserving escalation and personal contact; the long tail is best served by fully automated sequences that pursue every balance at negligible marginal cost; deteriorating accounts need faster escalation and early credit review.