A dunning letter is a formal written notice asking a customer to pay an overdue invoice. Effective dunning follows an escalation sequence: a friendly reminder in the first 30 days, a firm follow up at 31 to 60 days, an urgent notice at 61 to 90 days, and a final demand after 90 days that states what happens next. The four templates below cover each stage and can be sent by email, mail, or text.
A dunning letter is a formal written notice asking a customer to pay an overdue invoice. The most effective dunning follows a fixed escalation sequence: friendly at first, firm at 30 days, urgent at 60, and a final demand at 90 that states exactly what happens next.
This guide covers when to send each letter, what each one should say, and includes four copy ready templates you can use today, plus a text message version and a phone script for when letters stop working.
I see this constantly in wholesale and manufacturing companies. The invoice goes out, the due date passes, and nobody follows up for six weeks because everyone is busy shipping product. By the time the first real letter goes out, the customer has long since deprioritized you.
What is a dunning letter?
A dunning letter is not an invoice and not a statement. The invoice tells a customer what they owe. A statement summarizes their account. A dunning letter asks for payment that is late, and it exists to move money, not to inform.
The name comes from the old English verb dun, which meant to press someone persistently for payment. People have been dunning each other since the 1600s, and the word survives in accounting software today, where automated reminder sequences are still called dunning workflows.
One letter rarely collects on its own. What collects is the process: a fixed sequence of letters that escalate in tone and channel on a schedule your customers learn to take seriously. The templates below are the four steps of that sequence.
The dunning escalation timeline
| Stage | Days overdue | Tone | Channel | Goal |
|---|---|---|---|---|
| Reminder | 1 to 30 | Friendly | Assume oversight, make paying easy | |
| Firm follow up | 31 to 60 | Professional, direct | Email, then text | Establish urgency, ask what is wrong |
| Urgent notice | 61 to 90 | Formal | Email and phone | Involve senior contacts, state consequences |
| Final demand | 90+ | Formal, final | Letter and email | Last chance before collections or legal steps |
The sequence matters more than any single letter. Collection industry data has shown for years that the odds of recovering an overdue invoice fall as it ages, to roughly 70 percent at three months past due and about half at six months. Every stage in the table exists to keep an invoice from reaching the next one. The friendly reminder catches honest oversights, which is most late payments. The firm follow up surfaces disputes and cash problems while they are still solvable. The urgent notice gets the attention of someone senior enough to release payment. The final demand protects your right to escalate. Skip a stage, or send letters at random, and customers learn that your due dates are suggestions.
Dunning letter templates for every stage
Replace the bracketed fields and these are ready to send.
Stage 1: Friendly reminder (1 to 30 days overdue)
Subject: Overdue: Invoice #[number] for $[amount]
Hi [first name],
Just a friendly note that invoice #[number] for $[amount] was due on [date] and we have not received payment yet. Chances are it simply slipped through, it happens to everyone.
You can pay here: [payment link]. I have attached the invoice again for convenience.
If payment is already on the way, please disregard this note. If anything on the invoice looks off, reply and we will fix it.
Thanks, [your name]
Stage 2: Firm follow up (31 to 60 days overdue)
Subject: Second notice: Invoice #[number] for $[amount], now [X] days overdue
Hi [first name],
Invoice #[number] for $[amount] is now [X] days past due. We sent a reminder on [date of first letter] and have not heard back.
Please pay today using this link: [payment link]. If something is preventing payment, a dispute, a cash timing issue, a missing PO number, reply to this email and we will work it out. We would much rather solve a problem than keep sending letters.
Under our payment terms, balances past [X] days may accrue late fees of [rate].
[your name] [title, company]
Stage 3: Urgent notice (61 to 90 days overdue)
Subject: Urgent: Invoice #[number] for $[amount], [X] days past due
Hello [name],
Despite previous notices on [date] and [date], invoice #[number] for $[amount] remains unpaid at [X] days past due.
We need payment or a payment plan agreement by [specific date]. Without one, we will place the account on credit hold, which pauses [new orders, service, shipments].
Payment link: [payment link]. To discuss a payment plan, call [phone number] or reply to this email.
[your name] [title, company]
At this stage, send the letter to a second, more senior contact as well. The person receiving your reminders is often not the person who can release payment, and a controller or CFO usually does not know the invoice exists until you tell them.
Stage 4: Final demand (90+ days overdue)
Subject: Final demand: Invoice #[number] for $[amount]
Hello [name],
This is a final demand for payment of invoice #[number] for $[amount], now [X] days past due. We have sent [number] notices since [date of first notice] without resolution.
If payment is not received by [specific date, 7 to 10 business days out], we will refer this account to a collections agency and suspend all services. This may affect your company's trade credit standing.
Payment link: [payment link]. This outcome is avoidable. If you contact us before [date], we can still arrange a payment plan.
[your name] [title, company]
Dunning by text and phone
Letters and email are the backbone, but after two unanswered emails the channel is the problem, not the message.
Text message (use at stage 2 or 3):
[Company]: Invoice #[number] for $[amount] is [X] days overdue. Pay here: [link]. Questions? Call [phone number].
Phone script (stage 3):
Open with the specific invoice, not small talk: "Hi [name], this is [your name] from [company]. I am calling about invoice #[number] for $[amount], which is [X] days past due." Then follow the branch that matches their answer.
If they say payment is coming: "Great. Can I note a date on our side? I will hold further notices until [date]." Confirm the date by email the same day, and restart the sequence if the date passes.
If they never received the invoice: "No problem, I will resend it right now while we are on the phone. Can you confirm the best email?" Stay on the line until they confirm it arrived.
If they dispute the invoice: "I want to get that fixed. Tell me exactly what looks wrong and I will have a corrected invoice or an answer to you by [date]." Log the dispute and pause dunning on the disputed portion only. The undisputed balance stays in the sequence.
If there is no answer: leave a message with the invoice number, the amount, your callback number, and a specific deadline. Follow up by email the same day referencing the voicemail.
Legal considerations in the US and Canada
Two things first: this is general guidance, not legal advice, and it covers businesses collecting their own B2B invoices, which is a lighter regime than consumer debt collection.
In the United States, the FDCPA mainly governs third party agencies collecting consumer debts. A business collecting its own commercial invoices generally sits outside it. State laws still apply, and text messages are the sharp edge: the TCPA requires prior consent before you text a customer, so collect that consent in your contracts or onboarding.
In Canada, collection practices are regulated at the provincial level, and those rules are aimed mostly at licensed collection agencies rather than creditors collecting their own invoices. CASL governs commercial electronic messages, so the safe practice is the same as in the US: get consent for email and text outreach during onboarding, and keep records of it.
The advice that holds everywhere: state facts, never threaten an action you do not intend to take, keep a record of every notice you send, and move disputed amounts out of the dunning sequence until the dispute is resolved. If a balance is large or a customer goes silent after a final demand, spend an hour with a lawyer before you improvise.
What to do when dunning letters stop working
Stop sending letters when the final demand deadline passes without payment or contact. More letters after a final demand teach the customer that your deadlines are soft, and that lesson costs you on every future invoice too.
The decision at that point is a handoff. A collections agency typically keeps 25 to 50 percent of what it recovers, which sounds painful until you compare it with recovering nothing. Agencies make sense for larger balances where the relationship is already gone. For small balances, the math usually favors writing it off, moving that customer to prepayment terms, and spending your energy on invoices you can still save.
The full decision framework, including how to choose an agency and what to hand them, is in our guide on when to send invoices to collections.
Automating your dunning process
Everything above works manually if you have a dozen open invoices. At fifty or a hundred, it breaks in predictable ways. Someone forgets the day 30 letter. The tone jumps from friendly to furious because a different person wrote it. A customer who paid yesterday gets a final demand today.
Yonovo runs the whole sequence automatically. You define the timeline once, and reminders go out on schedule across email, text, and automated voice calls, escalating exactly the way this guide describes. The system checks QuickBooks or your accounting platform before every send, so a payment this morning means no letter this afternoon.
TDG put its collections on this kind of sequence and cut manual follow ups by 80 percent while reducing DSO by 15 days. If you want your dunning process to run like that, book a demo.
If you are building the sequence by hand first, start with our invoice reminder templates for the early stages, then measure your progress with our guide on how to reduce DSO.
Frequently Asked Questions
What is a dunning letter?
A dunning letter is a formal written notice sent to a customer who has an overdue invoice, asking them to pay. Dunning letters escalate in tone as the invoice ages, starting with a friendly reminder and ending with a final demand that states the consequences of continued nonpayment, such as referral to a collections agency.
Why is it called a dunning letter?
The word comes from the 17th century English verb dun, meaning to demand payment of a debt persistently. A dunning letter is simply a letter that duns. The term survives today in accounting and AR software, where automated reminder sequences are still called dunning workflows.
Is a dunning letter a legal document?
A dunning letter is not a legal filing, but it creates a written record of your collection attempts, which matters if the debt later goes to a collections agency or court. Final demand letters often reference next legal steps. Consult a lawyer for situations involving large balances or disputed debts. This article is general guidance, not legal advice.
When should you send the first dunning letter?
Send the first dunning letter within a week of the invoice becoming overdue. The earlier the first contact, the higher the collection rate. Many teams also send a courtesy reminder a few days before the due date, which is technically not dunning but prevents much of it.
How many dunning letters should you send before collections?
Most B2B teams send three to five dunning letters over 90 to 120 days before referring the account to a collections agency. The exact number matters less than consistency: a documented sequence with clear escalation at each stage collects more than sporadic aggressive letters.
Can dunning letters be automated?
Yes. Modern AR automation platforms send dunning sequences automatically based on invoice age, switching channels between email, text, and voice as the invoice gets older, and stopping the moment payment arrives. Automation makes the sequence consistent, which is what actually improves collection rates.
