Creating a professional invoice is only half the job. How you send it is equally important. A poorly-worded email, a confusing subject line, or a missing attachment can delay your payment by days or even weeks. A well-crafted invoice email gets read, processed, and paid — fast.

This guide gives you the exact formula for sending invoices by email, including word-for-word subject lines, email bodies, and follow-up templates.

Step 1: Always Send Your Invoice as a PDF

Before we talk about the email itself, let's be clear about the file format: always send your invoice as a PDF. Never send:

A Word (.docx) file — clients can accidentally edit it
An Excel file — formatting breaks on different versions
A photo or screenshot — extremely unprofessional
A Google Docs link — requires the client to sign in

A PDF is universally readable, cannot be accidentally edited, looks identical on every device, and can be printed or archived with a single click. FluxInvoice downloads your invoice directly as a PDF — no conversion needed.

Step 2: Write the Perfect Subject Line

Your subject line determines whether your email gets opened immediately or buried in a busy inbox. The perfect invoice email subject line contains three things:

The word "Invoice" (so it is instantly recognizable to AP departments)
Your invoice number (for easy reference)
The due date (creates urgency)

Examples of great invoice subject lines:

Invoice #INV-047 from [Your Name] — Due October 15
Invoice #INV-047 | [Project Name] | Due October 15, 2026
[Your Business] Invoice #INV-047 — $1,250 Due October 15

Examples of bad subject lines to avoid:

"Invoice" (too vague)
"Payment request" (unclear)
"Hey, here is my invoice!" (too casual for accounting departments)
No subject line (automatic spam signal)

Step 3: Write a Short, Professional Email Body

The email body does not need to be long. Your invoice has all the details. The email just needs to:

Greet the client by name
State the invoice number, amount, and due date in 1-2 sentences
Mention the attachment
Invite questions
Say thank you

Template 1: Standard Invoice Email

Subject: Invoice #INV-047 from [Your Name] — Due October 15

Hi [Client Name],

Please find attached Invoice #INV-047 for [amount], due on October 15, 2026, for [brief description of work, e.g., "the website redesign project completed in September"].

Payment details are included on the invoice. Please feel free to reach out if you have any questions.

Thank you — it has been a pleasure working with you!

Best regards,
[Your Name]
[Your Email]
[Your Phone]

Template 2: Invoice After Project Delivery

Subject: [Project Name] Delivered + Invoice #INV-047

Hi [Client Name],

I hope you are happy with the [project deliverable] — it was a great project to work on! I have attached Invoice #INV-047 for [amount], due by [date].

If you need anything adjusted or have any questions, please let me know. Otherwise, you can find payment details on the invoice.

Thanks so much!

[Your Name]

Step 4: Follow Up Automatically

Set a reminder in your calendar for the day before the invoice is due, then one day after, then one week after. Consistent, professional follow-up is the single most effective thing you can do to get paid on time.

Day-before reminder template:

Subject: Reminder: Invoice #INV-047 due tomorrow

Hi [Client Name],

Just a quick reminder that Invoice #INV-047 for [amount] is due tomorrow. Please let me know if you need anything from my side.

Thank you!

[Your Name]

Pro Tips for Invoice Emails

Send from a professional email address. Invoices from a Gmail or Hotmail address look less legitimate than invoices from yourname@yourdomain.com.
CC the right person. If you know the client has an accounts payable department, CC them directly.
Send it immediately. Send the invoice the same day you deliver the work. Every day you wait is a day the client moves on to other things.
Do not bury the invoice. Attach it to the very first email — not a follow-up. Clients should not have to ask for it.

Create a Professional PDF Invoice in 60 Seconds

Before you can send an invoice by email, you need to create one. FluxInvoice's free invoice generator lets you create a beautifully-designed, professional PDF invoice in under 60 seconds — with no sign-up required and no watermarks.

Create your invoice now and download the PDF →

How to Send an Invoice by Email Professionally (With Templates)