Before You Send: A Pre-Send Checklist
Before attaching the invoice to an email, verify:
- Invoice is in PDF format — not Word, not editable
- Invoice number is correct and sequential
- Client name and address are exactly right
- All line items match the agreed scope of work
- Totals and tax are calculated correctly
- Payment due date is included as a specific calendar date
- Your bank details or payment link are visible
- PO number is included if the client requires one
This 60-second check catches most errors before the client sees them. An error-free invoice needs no correction email and gets processed without delay.
The Invoice Email: What to Include
Subject Line
The subject line should include the invoice number and a brief description so it's immediately identifiable when the client searches their inbox. Accounts payable teams often search by invoice number, so including it in the subject line is practical, not just courteous.
Good subject lines:
- Invoice #2026-047 — Website Redesign Project — [Your Business Name]
- Invoice INV-0032 — £2,400 — Due 15 June 2026
- [Your Business Name] Invoice #1045 — May Retainer
Avoid vague subjects like "Payment" or "Invoice attached" — these can look like spam and give the client no useful information at a glance.
Email Body
Keep the covering message short and functional. Your client does not need a summary of everything the invoice covers — that's what the invoice is for. The email should:
- Greet the recipient by name
- Confirm what the invoice is for (one sentence)
- State the amount and due date
- Confirm how to pay
- Invite questions
- Close professionally
Invoice Email Template
Subject: Invoice #[NUMBER] — [PROJECT NAME] — [YOUR BUSINESS NAME]
Hi [Client Name],
Please find attached Invoice #[NUMBER] for [brief description of work], totalling [£AMOUNT] and due on [DATE].
Payment can be made by bank transfer to the details on the invoice. If you have any questions about the invoice, please don't hesitate to get in touch.
Thank you for your business.
[Your name]
[Your business name]
[Phone number]
This template works for the vast majority of invoices. It's direct, professional, and gives the client everything they need without requiring them to read three paragraphs before they find the amount.
Where to Send the Invoice
Always confirm the correct recipient before sending, especially for corporate clients. The person you worked with may not be the person who processes payments. Many large companies have a dedicated accounts payable email (e.g. ap@company.com or accounts@company.com).
Ask at the start of every engagement: "Who should I send my invoice to, and is there a specific email address for billing?" This simple question can save weeks of routing delays.
Follow-Up Schedule for Unpaid Invoices
A consistent follow-up process is the single most effective change most small businesses can make to improve their payment speed. Here's a practical schedule:
2–3 Days Before Due Date: Friendly Reminder
A brief, non-accusatory nudge. Most clients who receive this pay before the due date.
Subject: Reminder — Invoice #[NUMBER] Due [DATE]
Hi [Name],
Just a quick reminder that Invoice #[NUMBER] for [£AMOUNT] is due on [DATE]. Please let me know if you need anything from my side to process payment.
[Your name]
Due Date (If Unpaid): Prompt
Send on the due date itself if you can see the invoice hasn't been paid. Keep it brief and factual.
Subject: Invoice #[NUMBER] — Due Today
Hi [Name],
Invoice #[NUMBER] for [£AMOUNT] is due today. Please let me know if payment has been made or if there's anything I can do to help process it.
[Your name]
7 Days Overdue: Follow-Up
Firmer in tone, but still professional. Reference the original invoice clearly.
Subject: Overdue Invoice #[NUMBER] — [£AMOUNT]
Hi [Name],
I'm following up on Invoice #[NUMBER] for [£AMOUNT], which was due on [DATE] and remains unpaid. Could you please confirm when I can expect payment, or let me know if there's a problem I can help resolve?
[Your name]
14 Days Overdue: Call
At this point, pick up the phone. An email is easy to ignore; a phone call is not. Keep the conversation professional and problem-focused: "I'm calling about Invoice [NUMBER] — I wanted to check there wasn't a problem with it on your end."
30+ Days Overdue: Formal Notice
Send a formal written notice stating the invoice number, original amount, days overdue, any applicable late payment interest (see our note on common invoicing mistakes regarding late payment clauses), and a deadline for payment before you escalate further.
Using a Professional Email Address
Sending invoices from a branded email address (yourname@yourbusiness.com) is more professional than a Gmail address and reduces spam filtering risk. Domain-based email is inexpensive — most domain providers include email hosting, and Google Workspace starts at around £5/month for a professional email address.
If you can't set up a custom email immediately, at minimum use a professional Gmail address — firstname.lastname@gmail.com is more credible than a creative nickname.
Should You Use Invoice Software with Email Tracking?
Some invoicing platforms offer email tracking — notifications when your invoice email has been opened. This is useful context: if you can see the client opened the invoice 5 times but hasn't paid, you know the problem isn't that they haven't received it.
However, for most freelancers, this level of detail isn't necessary. A clear invoice, a polite follow-up process, and good client relationships are sufficient to maintain healthy payment rates.
Create a Professional Invoice to Send Today
Our free invoice generator produces a professional PDF invoice ready to attach to your email in under 2 minutes.
Build Your Invoice →Summary
Send invoices as PDF attachments with a clear subject line including the invoice number. Keep the covering email brief — state the amount, due date, and how to pay. Follow up with a reminder 2–3 days before due, again on the due date if unpaid, and escalate at 7, 14, and 30 days overdue. The templates above give you a framework you can reuse for every client — consistent, professional, and effective.