Past Due Notices: Templates for Late & Overdue Payment Letters

A past due notice is one of the most effective ways to follow up on unpaid invoices and protect your cash flow.

Getting paid by your customers is critical. When payments are delayed, businesses risk cash flow issues and increased collection costs. The longer an invoice remains unpaid, the lower the chances of recovering it.

This is why having a clear and structured approach to late payment letters is essential. While emails are often used for reminders, formal letters can add a stronger sense of urgency and help prompt faster payment. In this guide, you’ll learn:

• What Is a Past Due Notice?

• Past Due vs Overdue: Is There a Difference?

• When Should You Send a Late Payment Letter?

• The Right Tone for Payment Reminders

• What to Include in a Past Due Notice?

• Past Due Letter Templates

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What Is a Past Due Notice?

A past due notice is a message sent to customers when an invoice has not been paid by its due date. It is also commonly referred to as a late payment letter or payment reminder.

For invoices, "past due" refers to payments not made by their agreed-upon due date, signaling an overdue balance requiring immediate attention. Delayed payments can lead to late fees, interest charges, or strained business relationships. While companies often use standard payment terms, like 30 days post-invoice, businesses may negotiate flexible terms or payment plans for regular clients.

Under the European Late Payment Directive, enterprises must pay invoices within 60 days unless alternative terms are agreed. Beyond 60 days, a statutory interest of at least 8% above the European Central Bank’s reference rate and a €40 minimum compensation charge apply.

For startups, promptly addressing past due invoices is vital for maintaining healthy cash flow and strong client relationships. This makes it essential to have a clear late payment letters strategy for addressing overdue payments effectively.

Past Due vs Overdue: Is There a Difference?

The terms are often used interchangeably, and in most business contexts they mean the same thing: a payment that was not made by its agreed due date. But there are some subtle distinctions worth knowing, particularly if you are building a structured collections process.

"Past due" tends to appear in formal billing and collections contexts, particularly in the US. It refers specifically to an invoice that has crossed its payment deadline without being settled. You will see it on billing statements, collection letters, and AR aging reports, where invoices are typically categorised by how far past due they are: 1 to 30 days, 31 to 60 days, 61 to 90 days, and 90 days or more.

"Overdue" is broader and more commonly used in everyday business language. It carries the same meaning when applied to invoices but is less tied to formal collections terminology. In practice, finance teams use both terms depending on context: overdue in internal discussions and reporting, past due in formal customer-facing communications.

Some businesses also draw a distinction based on severity. An invoice that is a few days late is overdue. An invoice that is 60 or 90 days past due with no response is a different problem entirely, one that typically requires a shift in tone, a more formal letter, and a clearer statement of next steps. That progression is worth building into your collections process from the start, so every overdue invoice gets the right level of attention at the right time.

For practical purposes, a past due notice and an overdue payment notice are the same document. What matters more than the label is the structure behind it: how many notices you send, at what intervals, and what escalation looks like if payment still does not arrive.

When Should You Send a Late Payment Letter?

Sending a past due notice or late payment letter works best when you have already tried to contact your customer about their late payment by email or phone.

A past due notice is a more formal step in your collection process. It helps reinforce the importance of the situation and shows that you are taking the delay seriously.

Knowing exactly when to send one depends on your overall payment reminder strategy. Some businesses prefer to send a late payment letter once an invoice is a few weeks overdue, while others reserve it for later stages before escalation.

As a general guideline, you can follow a structured approach:

• 1 to 7 days overdue: send a friendly payment reminder

• 15 to 30 days overdue: send a past due notice

• 30 to 60 days overdue: send a more formal late payment letter

• 60 to 90 days overdue: send a final notice before escalation

Using a clear timeline like this helps you stay consistent and ensures that no overdue invoice goes unaddressed.

The Right Tone for Payment Reminders

A late payment letter should start as a polite reminder and become more assertive as the payment delay increases. This applies to both collection letters and payment reminder emails.

In the early stages, your tone should remain friendly and professional. The goal is to remind your customer of the outstanding invoice while preserving the relationship.

As time goes by and the invoice becomes more overdue, your message should become firmer. You can clearly state the amount due, highlight how late the payment is, and outline the next steps if payment is not received.

Since letters are generally seen as more formal than emails, it is important to keep a professional tone throughout. Using clear and direct language helps reinforce the seriousness of the message.

Your tone should also reflect the relationship you have with your customer. A long term customer may respond better to a more understanding approach, while a new customer may expect a more formal communication.

In practice, it is best to have several payment reminder templates adapted to different situations. This allows you to communicate effectively while maintaining strong customer relationships.

What to Include in a Past Due Notice?

Regardless of the tone and the context in which you send your past-due notice letter, there are a few elements that should always be included: 

• Personal information: Includes the name and company name of your contact, as well as your business’ name. Being personal means ensuring your contact knows the letter is addressed to them (i.e. it's not a mistake) and also serves as a reminder of the services or products you’ve provided. 

• Contact information: include your address, email, and phone number so they can easily contact you if needed. 

• The original invoice: print and send a copy of the original invoice so they can refer back to it. Also include the invoice number and the amount due in the letter requesting payment (if there is more than one, make a list). 

• The original invoice due date: highlight the number of days past-due by including the due date of the original invoice.

• The past-due invoice: if you charge a late fee, include it in an updated invoice that you attach to the letter and whose total amount and number you have referenced in the letter as well.

  
  

• Your payment methods: include specific instructions on how your customer can pay you right away. This could be a link for online payment where they can pay via credit card or your bank account number. The more payment options, the better. 

• A payment plan (optional): suggest a payment plan with weekly or monthly payments to make it easier for your clients to pay you. 

• Your next step: remind them of the next step you will take if they don’t pay within a certain time frame - limiting access to your solution or service, or taking legal action. This could also include a warning around accumulating late payment fees (or a mention that you'll have to use a collection agency). You can cite your T&Cs and/or your contract.  

Past Due Letter Templates

Now that you know how, when and what to include in a letter requesting payment, let’s have a look at some specific payment reminder templates.

Whether you're sending a simple payment reminder, a more formal past due invoice letter, or a final notice before escalation, the templates below cover the most common scenarios.

Payment Reminder Letter Template for New Customers

With new customers, you want to make sure they’ve understood how to work with you and how to pay you. It might be that they didn’t get your payment terms right or simply that they’ve forgotten to pass your invoice to the relevant person in their company.  

Regardless of the reason, it’s a good idea to remind them of what your processes are and to clearly lay out your payment terms and methods. 

You can also include a prompt to automate their future payments, which makes sense if you have a subscription-based business model.

We also encourage you to open the conversation by mentioning they can contact you if they have any questions about how your business operates. 

Here’s a template letter you can use: 

Past Due Invoice Letter Template (30 Days Overdue)

When an invoice is 30 days or more overdue, it’s important to move from a simple reminder to a more structured follow-up.

At this stage, non-payment is typically due to one of two reasons:

• The invoice has been overlooked or delayed internally

• The customer may be experiencing cash flow constraints

Either way, sending a more formal past due invoice letter helps bring urgency to the situation and encourages a response.

Depending on your business model, it can also make sense to involve your sales representative or account manager earlier in the process to help resolve the situation and maintain the relationship.

Here’s a template letter you can use: 

Past Due Invoice Letter Template (60 Days Overdue)

By 60 days, the situation has moved beyond a simple oversight. Most customers who intend to pay will have done so by now. This letter should make clear that you are tracking the delay closely and that further action is coming if payment is not received within a specific timeframe.

Keep the tone professional but direct. Avoid lengthy explanations. State the amount, the number of days overdue, and the deadline clearly.

Here is a template you can use:

Past Due Invoice Letter Template (90 Days Overdue)

At 90 days, this is a final notice. The tone should be firm and short. There is no need for lengthy context at this point. The customer has received multiple communications. This letter documents that a final opportunity to pay has been given before escalation.

Here is a template you can use:

Final Notice Letter for Payment (Before Legal Action)

The last notice letter is the ultimate way to bring attention to the non-payment of an overdue invoice. If you have a red stamp handy, this is when you should use it! 

These final notice letters should be used in only the most dire situations, when you’ve tried repeatedly to contact the customer over a long period of time (say, 60 or 90 days overdue).

In most situations, this letter would solve matters quickly. If not, be ready to follow through with concrete actions. 

Here’s a template letter you can use: 

Want to see the collection emails you should send before moving to formal notices? Download them below.

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