What should a dunning letter include?

The invoice number, the amount owed, the original due date, how many days it is overdue, a clear way to pay, and a deadline or next step. Later letters in the sequence also state what happens if the balance stays open.

How many dunning letters should you send?

A common sequence is three to four letters, starting with a polite reminder near the due date and escalating to a final notice around 45 to 60 days past due before the account moves to a person or collections.

May 7, 2026 · Rex

What is a dunning letter? Examples and templates

A dunning letter is a written notice that reminds a customer to pay an overdue invoice. Here is what to include, a stage-by-stage sequence, and ready-to-use examples.

A dunning letter is a written notice that reminds a customer to pay an invoice that is due or overdue. It names the specific invoice, states the amount and the days past due, and asks for payment by a set date. Letters run as a sequence that escalates in tone, from a gentle first reminder to a firm final notice.

A dunning letter is the unit. Dunning is the process that strings those letters together into a cadence. The letter does the persuading, so its wording matters. A good one is short, specific, and easy to act on. A bad one is vague, buries the ask, or sounds so harsh on the first contact that it sours a relationship over an invoice the customer simply forgot.

What to include in a dunning letter

Every letter in the sequence shares the same backbone, regardless of how firm it gets.

The invoice details. Number, amount, original due date, and current days overdue. Specificity makes the letter impossible to dismiss as a generic reminder.
A clear payment path. A payment link, portal, or bank details so the customer can act without hunting for how.
A deadline. A date by which you expect payment, not an open-ended "as soon as possible."
The next step. What happens if the balance stays open. Soft in early letters, concrete in later ones.
A line for disputes. An invitation to reply if something is wrong with the invoice, so a genuine issue surfaces instead of festering.

Dunning letter sequence

A standard sequence on net-30 terms runs three to four letters. The age triggers each one, and the tone climbs with the age.

Reminder. On or just before the due date. Assumes good faith.
First overdue notice. Three to five days late. Notes the invoice is past due.
Escalation notice. 15 to 30 days late. Firmer, names the days overdue, offers a payment plan.
Final notice. 45 to 60 days late. States the consequence, such as a credit hold or escalation to collections.

Dunning letter examples

Here are two letters from opposite ends of the sequence. Replace the bracketed placeholders with the real details.

Subject: Reminder: invoice [Invoice number] is due [Due date]

Hi [Customer name],

A quick reminder that invoice [Invoice number] for [Amount] is due on [Due date].

You can pay it here: [Payment link]

If you have already paid, thank you, and please ignore this. If anything looks off, just reply and we will sort it out.

Thanks,
[Your name], [Company name]

When to use this: as the first, friendly touch on or near the due date.

Subject: Final notice: invoice [Invoice number], [Amount] outstanding

Hi [Customer name],

This is a final notice for invoice [Invoice number] for [Amount], originally due [Due date] and now [Days overdue] days overdue.

Please pay in full by [Final due date]: [Payment link]

If we do not receive payment or hear from you by that date, the account will be escalated for further collection steps and a hold may be placed on new orders. We would much rather resolve this directly, so reply today if there is an issue we should know about.

Regards,
[Your name], [Company name]

When to use this: as the last automated touch before a person or a collection agency takes over.

Tips for effective dunning letters

Lead with the invoice, not pleasantries. The reader should see what this is about in the first line.
Keep it to a few sentences. Long letters get skimmed and the ask gets lost.
Reference the real context. If the customer raised a dispute or made a promise, the letter should reflect it, not pretend the account is generic.
Stop on a reply. A dispute or a promise to pay ends the automated chase. Carrying on regardless reads as careless.

How Rex writes and sends dunning letters

Rex moves past static templates. For each overdue invoice it composes a letter that references the actual account, the specific invoice, and any dispute or promise already on file, then sends it on the channel that customer reads. When the customer replies, Rex reads the response, acts on it, and adjusts or pauses the sequence rather than firing the next templated notice regardless.

The result is letters that feel written for the account, sent continuously across the whole ledger, with only the cases that need a human decision reaching a person. See how Rex runs collections end to end.

Frequently asked questions

What is a dunning letter?: A dunning letter is a written notice, by email or post, that reminds a customer an invoice is due or overdue and asks for payment. Letters usually run as a sequence that grows firmer as the invoice ages.
What should a dunning letter include?: The invoice number, the amount owed, the original due date, how many days it is overdue, a clear way to pay, and a deadline or next step. Later letters in the sequence also state what happens if the balance stays open.
How many dunning letters should you send?: A common sequence is three to four letters, starting with a polite reminder near the due date and escalating to a final notice around 45 to 60 days past due before the account moves to a person or collections.