A Guide to Writing Past Due Invoice Email

Dimitri Raziev07 Oct 202212 mins
A Guide to Writing Past Due Invoice Email


●       Whether you’re a business owner or you work in the finance department of a company, learning how to write a past-due invoice email is an essential task.

●       To write a past-due invoice email, you must follow 6 simple steps. The first step is to highlight your oldest overdue invoices; then you should write a clear email subject and a friendly opening paragraph.

●       When writing the body of the past due invoice email, be as succinct and direct as possible. Remember to attach a copy of the invoice to your email – and end it with a call to action.

●      If your customer is still not paying, you should escalate your invoice past due email and take legal action via a small courts claim. Furthermore, you should prevent this from ever happening again by investing in an automated AR solution.


Learning how to send an invoice past due email is an essential skill for any business owner. Whether you own a small-to-medium business or you’re the finance manager of a multinational company, you’ll have to come to terms with the fact that it is very likely that some of your payments will go unpaid after their past due date.

However, there’s no need to start panicking and worrying about your past-due invoices. In the vast majority of cases, overdue invoices will still be paid without having to recur to take any drastic action. More often than not, all it takes is sending a well-written invoice past due email or letter to your customer.

That being said, writing a past-due invoice letter or email is not something you can just master in five minutes. And that is exactly why we’ve put together this short guide on how to write a past-due invoice email in 6 simple steps.

How to Write a Past Due Invoice Email in 6 Simple Steps

For the uninitiated, an invoice past due is an invoice that has not been paid after the agreed due date. Most invoices usually have a past due date of 2-4 weeks upon receipt. But what if there is no past due date? In that case, it depends on each country’s law. For example, if a UK invoice is issued without a past due date, it will become past overdue on the 30th day after it was received.

Invoices are usually chased via emails instead of letters. There are plenty of clear reasons for this – apart from being a much faster means of communication, emails allow you to keep a traceable record of your back-and-forth with your customer. If your invoice dispute ever ends up being resolved in the small claims court, having textual evidence could be an invaluable asset.

Writing an invoice past due email is something that no one wants to do. To start with, having a past-due invoice in your books puts you in an awkward position. On the one hand, you don’t want to tarnish your professional relationships with your clients. But on the other hand, you need all of your invoices to be paid in order to remain a viable business with a healthy cash flow. So, what’s the best way forward if you find yourself in this situation?

Without a doubt, the best thing you can do is to write a professional, tactful and convincing invoice past due email that allows you to chase payment without putting your professional bond at risk. Let’s see how to do this in 5 simple steps:

1.    Highlight your oldest overdue invoices

The first step to recovering the money owed to you via invoice past due emails is to set up a clear plan of action. Firstly, you’ll need to start looking at all your overdue invoices from a reverse date of issue – that is, figuring out which are your oldest overdue invoices and who sent them. That way, you’ll chase your most urgent invoices first – in turn, increases the chances of getting your money back.

At this point, there’s one thing that ought to be clarified. Even if an invoice is past overdue by months, that’s not to say that your customer is acting in bad faith. In fact, most overdue invoices remain unpaid out of pure forgetfulness. You just need to take control of the situation and act in your best interest.

And don’t worry if you have past due invoices that are almost one year old. In the UK, old invoices can still be chased for payment until six years from the date it was received.

2.    Write a clear (but not threatening) email subject

Once you know which past-due invoices you need to chase first, it’s time to start writing your email chasers. Let’s begin with the most obvious starting point – the subject. As is the case with all kinds of emails, a good subject for a past-due invoice reminder needs to be straightforward, to the point and enticing. You want to make sure that your customer clicks on your email, not that you scare them away.

So, how do you catch your customer’s attention by using only a few words? In our opinion, it’s all about being clear and direct. After all, an email subject should convey your message in only a few words – meaning there’s no space to stick to convoluted politeness formulas.

Suffice it to say, being clear and direct doesn’t mean being rude. When you’re writing your past due invoice reminder, please do not write in capital letters under any circumstances. Remember that writing in capital letters is the email equivalent to shouting in real life. If you wish to get your message across clearly, there are better ways of doing this.

Basically, you need to arrive at a comfortable middle ground between being diplomatic and being assertive. If you’re worried about your relationship with your client and want to keep your email as tactful as possible, don’t worry. There’ll be plenty of time and space to sugar-coat things in the body of your past-due invoice email.

Here are the things that the subject for your past due invoice email should include:

-The phrase “overdue invoice” or an equivalent – such as “past due” or “unsettled” invoice

-Your invoice number – this is completely essential, as it’ll allow your customer to complete the payment rapidly

-Your company name (only if you are writing from a personal address)

-The word “reminder” or an equivalent noun – such as “notice”.

-If you don’t have enough space to include all these things, don’t worry – just ensure that the invoice number and the phrase “overdue invoice” are part of your email subject.

3.    Start with a polite opening paragraph

Even if an invoice is past overdue by months, rudeness is never an option. This piece of advice is as helpful for small-to-medium business owners as it is for finance managers working in a big company. If you’re the former, you’ll be well aware that getting good clients isn’t exactly easy. And if you’re the latter, you’ll know that your sales colleagues work hard to maintain valuable professional relationships with your customers. If you put additional strain on that relationship and the customer ends up breaking off the agreement, you’ll be the one to blame – and that is the last thing you want.

This means that you need to ensure that your past-due invoices letter is as courteous as possible. To do this, write a friendly and polite opening paragraph that makes your customer see that your working relationship is still fine in spite of the overdue invoice. 

The kind of opening you’ll use will always depend on the sort of relationship you have with the client. If you have a long-running rapport, it’s always a good idea to passingly mention a previous common topic of conversation – minor things such as the weather or football results.

And if your relationship with your client is not particularly friendly, don’t worry. Just keep things formal and polite with a good old “How are you?” or “I hope you are doing well”. Basically, your friendly reminder for a past due invoice should always do what it says on the tin – being friendly. Never jump straight into chasing an invoice without cooling things down with an amicable opening.

4.    Write a succinct and convincing body

Once you’ve written your opening paragraph, it’s time to get to the gist of your invoice past due email. And that is chasing your unpaid invoice. In this part of the email, try to keep things as formal as possible. Most importantly, remember that you will always need to include the following things:

-Invoice reference number

-What the invoice was for

-The date the invoice was sent

-The original date the invoice was due

-The number of days that the invoice is now overdue

-Payment forms

If this isn’t your first communication regarding an unpaid invoice with a particular client, you should also include a short and blunt statement introducing the possibility of legal action being taken if the invoice is not paid.

5.    Attach a copy of the past overdue invoice

To make things easier for your customer, make sure you always attach the past overdue invoice to your email – preferably in PDF format. That way, they won’t even have to dig into their records and trace the invoice back. To avoid confusion, you should also attach the original email you sent when the invoice was first sent. This is also a way of letting your customer know that your invoice still remains unpaid after a fairly long period of time.

6.    Close your email with a call to action

If you work in marketing or you’re just a very perceptive person, you will have noticed that most adverts end up with a call to action (CTA) that encourages the recipient to do something. Believe it or not, the CTA is an incredibly effective method to get your reader to do what you want them to – in this case, paying your past-due invoice.

Closing an invoice past due email with a CTA is not exactly playing mind games – in fact, it is a fairly common business practice. As this is a formal context, your CTA doesn’t need to be particularly enthusiastic or alluring. These are some valid CTAs examples to use at the end of your email:

-Please let me know once payment has been made so I can advise my sales team accordingly

-Please confirm your receipt of this past-due invoice

-Please confirm when this invoice will be paid in full

If you follow all of these steps, the most likely outcome is that your customer will immediately pay the overdue invoice in full. But what if you send yet another past-due invoice reminder and they still haven’t paid?

How to escalate an overdue invoice email

If your past due invoice has gone unpaid for more than three months and your customer is still ignoring you after more than eight past due invoice emails, it might be time to start legal action. But there are some things you can do before you take your customer to the small claims court. These are the steps you need to follow to escalate an unanswered past-due invoice email.

1.    Send a follow-up invoice past due email

Is your past-due invoice email still ignored after more than a week? In that case, you need to send your customer a stern follow-up invoice past due email. By doing this, you’ll be conveying a clear message – that is, that legal action will be considered if payment isn’t made in X days.

Remember to include every single detail we mentioned in the fourth and fifth steps of our past-due email sample – from the invoice reference number to a copy of the invoice in PDF format.

If your customer has ignored your follow-up email, you need to automatically change your mindset. At this point, it’s not about maintaining a good relationship with your customer anymore, but about making sure you get your money back.

Fortunately, taking legal action against unpaid invoices of below £10,000 is relatively simple in the UK. You just need to do the following two things:

Write a “letter before action” to formally inform your customer that you’ll be taking legal action if payment isn’t made in 14 days

-Head to the UK Government website to start your formal claim and take your customer to the small claims court.

-Once you’ve won your case, your customer will have to pay the invoice in full – plus interest and the small claims court’s fee.

3.    Make sure it doesn’t happen again

In business as in life, we aren’t born knowing everything. Instead, our knowledge grows as we learn from our mistakes. If you’ve had to go through the unpleasant experience of chasing and escalating an overdue invoice email, you’ll know that the last thing you want is for it to happen again.

Thankfully, there is a way of ensuring that spending night and day sending past-due invoice reminders doesn’t become the norm. And that is implementing an automated Accounts Receivable solution that instantly flags your outstanding invoices and sends personalised overdue invoice emails on a periodic basis.

Sounds like what you’re after? Then head to Kolleno and see the benefits of our automated AR solution for yourself with our free trial.

Frequently Asked Questions (FAQs)

What to say in an email about past due invoices?

When writing a past-due invoice email, you need to convey essential information in a succinct manner. These are the things you should always include – invoice number, a copy of the invoice, the number of days that the invoice is overdue, and payment forms.

How do you politely ask for overdue payment?

One of the hardest things about learning how to write an invoice past due email is striking the right balance between politeness and assertiveness. In our opinion, you should be particularly polite in the opening and closing parts of your past-due invoice email – but keep the actual payment request as formal as possible.

What happens when an invoice is a past due?

If an invoice hasn’t been paid after the past due date you set, you can start to claim interest on it. If it’s still not paid 30 days after the past due set, you can take your customer to the small claims court and get your money back.