How to Send an Invoice by Email
Creating the invoice is only half the job. How you send it — the subject line, the body, the timing, the follow-up — determines how quickly you actually get paid. Here's the complete guide.
The invoice email subject line
Your subject line determines whether the email gets opened immediately or sits unread. It needs to contain three things: the invoice number, a project reference, and the due date. This gives the client's accounts team everything they need to find, identify, and act on the invoice without opening it.
Subject line examples
Invoice #INV-047 — Website Redesign — Due 30 June 2026Invoice #INV-047 for Acme Corp — Due 30 June 2026Invoice #INV-047 — Due 30 June 2026Invoice attachedPlease find my invoicePayment dueVague subject lines like “Invoice attached” get buried. A subject line containing “Invoice #INV-047” can be searched, filtered, and found by the client's accounting team months later if needed.
Invoice email templates for every situation
Use these templates as starting points. Personalise the tone to match your relationship with each client — a first-time client gets a slightly more formal tone than a long-term one you've worked with for years.
Subject
Invoice #INV-047 — [Project Name] — Due [Date]Body
Hi [Client Name], Please find attached Invoice #INV-047 for [brief description of work], totalling [amount]. Payment is due by [due date]. You can pay via [bank transfer / PayPal / etc.]: [Your payment details here] Please use invoice number INV-047 as your payment reference. Thank you for working with me — it's been a great project. Let me know if you have any questions. Best, [Your name]
Subject
Reminder: Invoice #INV-047 due [Date]Body
Hi [Client Name], Just a quick reminder that Invoice #INV-047 for [amount] is due on [date]. If you've already sent payment, please ignore this message and thank you! Payment details: [Your payment details here] Let me know if you need anything from me. Best, [Your name]
Subject
Invoice #INV-047 — Payment OverdueBody
Hi [Client Name], I wanted to follow up on Invoice #INV-047 for [amount], which was due on [date]. If you've already arranged payment, thank you — please let me know so I can update my records. If not, I'd appreciate it if you could arrange payment at your earliest convenience using the details below: [Your payment details here] Please don't hesitate to reach out if there are any issues with the invoice. Best, [Your name]
Subject
Final Notice: Invoice #INV-047 — [Amount] OverdueBody
Hi [Client Name], This is a final notice regarding Invoice #INV-047 for [amount], which is now 14 days overdue. Please arrange payment by [new deadline — 7 days from now] to avoid further action. As noted in my payment terms, a [late fee rate] late fee applies to invoices overdue beyond [your grace period]. Payment details: [Your payment details here] If there is a specific issue with the invoice or the work, please contact me directly so we can resolve it. [Your name]
When to send your invoice email
Timing matters more than most freelancers realise. The same invoice sent on a Tuesday morning vs a Friday afternoon can have very different payment outcomes.
Send the invoice the same day you deliver
The moment a client marks a project as done mentally, paying for it becomes less urgent. Invoice immediately on delivery — don't wait until 'end of the week' or 'end of the month'.
Send on Tuesday, Wednesday, or Thursday
Monday mornings are buried in meetings and catch-up emails. Fridays get deprioritised before the weekend. Mid-week invoices are opened, processed, and paid fastest.
Send before noon in the client's timezone
Emails sent before noon are more likely to be actioned the same day. An invoice that arrives at 4pm often gets pushed to 'tomorrow' — which becomes next week.
Don't send invoices during client holidays
If you know your client's office is closed, wait until they're back. An invoice buried under a week of holiday emails gets missed.
Follow up within 24 hours of the due date
Don't wait a week to chase an overdue invoice. A message the day after the due date often results in same-day payment — the client simply forgot.
Should you attach a PDF or send a link?
The traditional approach is attaching a PDF to the email. This works fine but has a few downsides: attachments sometimes get flagged by spam filters, clients have to download and open a file, and there's no way to know if the invoice was actually viewed.
A modern alternative — used by tools like SwiftBill — is sending a public invoice link alongside (or instead of) the PDF. The client clicks the link, views the invoice in their browser, and can reference it any time without hunting through their downloads folder.
Best practice: send both. Attach the PDF for clients who prefer a file, and include the public link for anyone who finds it easier to view in a browser. This also gives you a permanent URL you can reference in follow-up emails.
Before you hit send — checklist
Create a professional invoice to send today
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