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Invoice email templates for sending and following up

An invoice email template to copy for sending, the due date and a follow-up, a short invoice message for text or WhatsApp, and how to attach the invoice.

5 min read
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01The short answer

What should an invoice email say?

An invoice email should identify the job and invoice number, state the amount due and agreed payment date, and tell the customer where to find payment instructions. Attach the invoice as a PDF and use a subject line the customer can search for later.

The templates below cover the first send, a reminder on the due date, a follow-up after it, and a short invoice message for a client you text. Replace every bracketed field. The example amount of £185.00 is fictional and matches our simple invoice example.

A message by text or WhatsApp has no subject line, so it puts the invoice number, amount and due date in its first sentence. Template 4 is written that way.

Before writing, check whether the customer asked for a supplier portal or a dedicated billing address. An email to your day-to-day contact may not reach the person who processes payments. Use the route you agreed when accepting the job.

02Send the invoice

Template 1: sending an invoice after a job

Subject: Invoice INV-2026-014 for [job description], due 30 September 2026

Hi [customer name],

Attached is invoice INV-2026-014 for [job description] completed on 16 September 2026. The amount due is £185.00 GBP, payable by 30 September 2026 as agreed.

Payment instructions are on the invoice. Please use INV-2026-014 as the payment reference.

If you need any detail corrected or an order reference added, please reply to this email.

Thank you,
[your name]
[business name]
[contact details]

Attach INV-2026-014.pdf before you press send. Open the attachment from the draft email to confirm it is the finished invoice, not an old version or another customer's file. If you have not created the PDF yet, follow our free invoice PDF guide.

Keep the subject factual. The invoice number and job description help someone find the message; an urgent label adds little when payment is not yet due. Do not promise a payment option that the invoice does not actually support.

03On the due date

Template 2: a reminder when payment is due

Subject: Payment due today: invoice [number] for [job]

Hi [customer name],

A quick reminder that invoice [number] for [job] is due today, [date]. The remaining balance is [amount and currency]. I have attached the invoice again for reference.

If you have already sent payment, thank you. Please let me know the payment date and reference so I can match it to the invoice.

If anything is holding up approval, please reply and I will help resolve it.

Thank you,
[your name]

Check your payment records before using this message. If the customer paid part of the invoice, state the remaining balance rather than copying the original total. Use “due today” only on the actual agreed due date.

A reminder should reduce the customer's work. Reattach the relevant document, keep the reference consistent and give them a clear way to raise a problem. There is no need to describe the whole job again.

04After the due date

Template 3: following up on an unpaid invoice

Subject: Payment update requested: invoice [number]

Hi [customer name],

I am following up on invoice [number] for [job], which was due on [date]. My records show a remaining balance of [amount and currency]. A copy is attached.

Could you confirm when payment is expected? If there is a query with the invoice or it needs to go to someone else, please let me know.

If payment has already been made, please send the date and reference so I can check.

Thank you,
[your name]
[contact details]

Use this after checking the due date and payments received. Avoid guessing why the customer has not paid. A missing order number, a disputed line and a message sent to the wrong address need different responses; this wording lets the customer tell you which problem to solve.

Keep the follow-up in the original email thread where practical. It preserves the context and avoids leaving the customer with several unrelated messages about the same invoice. This template does not add interest, fees or new payment terms. If the follow-ups go unanswered, a letter before action is the formal step before a court claim, and it has rules of its own.

05A text message

Template 4: a short invoice message to a client

For a client you normally text, send two sentences and the PDF: what the invoice is for, how much, and by when. Everything else is on the invoice.

Hi [customer name], here is invoice INV-2026-014 for [job description]: £185.00, due 30 September 2026. Payment details are on the invoice; please use INV-2026-014 as the reference. Thanks, [your name]

Send the PDF in the same chat, straight after the message, so the two stay together. A photo of a printed invoice is harder to read and to file than the PDF itself.

For a reminder, keep the same shape and change the first sentence: "Hi [customer name], a reminder that invoice [number] for [job] is due today, [date]." Text suits a homeowner. A business with an accounts department will usually want email, to the address it gave you for invoices.

06Attaching it

How do you attach an invoice to an email?

Save the invoice as a PDF, then use your email’s attach button (usually a paperclip) to add that file before you send. On a phone, you can also open the PDF and share it straight into your mail app.

Name the file after the invoice, such as INV-2026-014.pdf, so the customer can find it in their downloads and their accounts team can match it to a payment. "Document1.pdf" helps nobody.

Send a PDF rather than a Word file or a spreadsheet. A PDF looks the same on every screen and cannot be edited by accident. Then open the attachment from your sent folder once, to check it is the finished invoice for the right customer.

07Before you send

A final check for each message

Match five details across the subject, message and PDF: invoice number, customer, job, balance and due date. Then check the recipient and attachment. If payment instructions have changed, confirm the change through a contact route the customer already knows.

The UK's Small Business Commissioner invoicing guide recommends clear descriptions, purchase order references where supplied and terms agreed in advance. Those practical checks inform this checklist; the email wording above is an original example.

Invoice Koi's free browser generator creates the document. You save the PDF and send it through your own email. It does not send these reminders automatically. Keep the sent message and your saved invoice together so the next follow-up starts from a reliable record.

While you are here

Put the example to work

Enter your own details in the free browser generator, check the finished document and save your PDF.

Make an invoice free

On Google Play now. Coming soon to iPhone. Have the app? Open it

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