Invoice Email: Templates, Subject Lines + Best Practices (2025)
Over 90% of invoices are sent by email β yet most freelancers and small businesses send them badly. A poorly written invoice email gets ignored, forgotten, or lost in a cluttered inbox. This guide shows you exactly how to write invoice emails that get opened, read, and paid.
The perfect invoice email subject line
The subject line determines whether your email gets opened or overlooked. It needs to be instantly clear, professional, and reference something the client can identify. Here are three formats that work:
Standard (recommended)
Invoice INV-2025-042 β Website Redesign β Due 24 May 2025
Includes invoice number, project name, and due date. The client knows exactly what it is before they open it.
Minimal (for ongoing clients)
Invoice for May β [Your Company Name]
Works for recurring invoices where the relationship is established. Less formal but still clear.
Action-oriented
Payment due 24 May β INV-2025-042 attached
Puts the due date first. Creates a sense of urgency without being aggressive.
Invoice email template 1 β Standard
This is the go-to template for most invoice emails. Professional, brief, and contains everything the client needs to process payment.
TO:
accounts@clientcompany.com
SUBJECT:
Invoice INV-2025-042 β Branding Project β Due 24 May 2025
Hi Sarah,
Please find attached invoice INV-2025-042 for the brand identity project completed on 10 May 2025.
Amount due: Β£2,400
Due date: 24 May 2025 (Net 14)
Payment: BACS transfer to Barclays Β· Sort: 20-00-00 Β· Acc: 12345678
Reference: INV-2025-042
If you have any questions about this invoice, please don't hesitate to get in touch. I'll follow up if I haven't heard from you by the due date.
Thank you for the work β it was a pleasure working on this project.
Best,
[Your Name]
[Your Business Name]
[Phone]
Invoice email template 2 β Project milestone payment
For projects split into phases, your invoice email needs to clearly reference which milestone is being billed and what's been delivered.
SUBJECT:
Invoice INV-2025-018 β Phase 2 Complete β E-Commerce Project
Hi James,
Phase 2 of the e-commerce build is now complete. Please find invoice INV-2025-018 attached.
This invoice covers: Product catalogue integration, shopping cart functionality, and payment gateway setup (as per our agreed scope in the contract dated 3 April 2025).
Amount due: Β£3,500 + VAT (Β£700) = Β£4,200 total
Due date: 7 June 2025
Payment: BACS to NatWest Β· Sort: 60-00-04 Β· Acc: 99887766
Phase 3 (testing & launch) is on track to begin next week as planned.
Let me know if you have any questions.
Best,
[Your Name]
Invoice email template 3 β Recurring / retainer invoice
For monthly retainers, keep the email short. The client already knows what they're being billed for β just confirm the amount and period.
SUBJECT:
Monthly Invoice β June 2025 β Social Media Retainer
Hi Emma,
Please find your June 2025 retainer invoice attached (INV-2025-JUN-R04).
Amount: Β£1,200
Due: 8 June 2025
Payment: Monzo Β· Sort: 04-00-04 Β· Acc: 11223344
Quick note β we had a great month on engagement for the Instagram account. I'll include the full analytics in the monthly report on Friday.
Thanks as always,
[Your Name]
5 common invoice email mistakes
β Mistake: No attachment
β Fix: Send the invoice as a PDF attachment (or a direct link to a hosted invoice). Never just send an email saying 'please pay' without the actual invoice.
β Mistake: No subject line structure
β Fix: A vague subject like 'Invoice' or 'Payment' gets archived by spam filters and ignored by accounts teams. Always include the invoice number and due date.
β Mistake: Wrong recipient
β Fix: Many businesses have a dedicated accounts payable email (accounts@, finance@, billing@). Always ask your client early: 'Who should I address invoices to?' Sending to the wrong person delays payment by days or weeks.
β Mistake: No payment details in the email body
β Fix: Don't make the client open the PDF to find your bank details. Put the amount, due date, and payment method directly in the email body. Reduce friction, get paid faster.
β Mistake: Not following up
β Fix: Most freelancers send one email and hope. Data shows that 40% of late invoices are resolved with just a single follow-up. Set a reminder, or use Chaser to automate the sequence.
When to send invoice emails
Timing affects open rates and how quickly accounts teams process your invoice. Research on B2B email engagement shows:
β Best times to send
- β’ Tuesday, Wednesday, Thursday
- β’ 9amβ11am (when inboxes are being processed)
- β’ First of the month (for retainers)
- β’ Same day as delivery (for project invoices)
β Avoid sending
- β’ Friday afternoon (buried over the weekend)
- β’ Monday morning (swamped by other emails)
- β’ Public holidays
- β’ Last day of the month (accounts teams are closing books)
Invoice follow-up email sequence
If your invoice isn't paid by the due date, here are the three follow-up emails to send β in order. Keep them short. Escalate the tone gradually.
Reminder 1 β Day 1 after due date
Subject: Gentle reminder β Invoice INV-2025-042 due yesterday
Hi Sarah, just a quick note to flag that invoice INV-2025-042 (Β£2,400) was due yesterday. Please could you let me know when I can expect payment? Details are in the attached invoice. Thanks!
Tone: Friendly β assume it's an oversight
Reminder 2 β Day 7 after due date
Subject: Invoice INV-2025-042 β 7 days overdue β please advise
Hi Sarah, I wanted to follow up again on invoice INV-2025-042 (Β£2,400), now 7 days overdue. Could you give me an ETA for payment, or let me know if there's an issue I can help resolve? I'd appreciate a quick reply.
Tone: Firm but still professional β request a response
Reminder 3 β Day 14 after due date
Subject: URGENT: Invoice INV-2025-042 β 14 days overdue
Hi Sarah, this is my third chase for invoice INV-2025-042 (Β£2,400), now 14 days overdue. Under the Late Payment of Commercial Debts Act 1998, I am entitled to charge statutory interest on this amount. Please pay within 7 days to avoid further action. If there is a dispute, please contact me immediately.
Tone: Serious β references legal entitlements
How to CC/BCC effectively
β CC the accounts department
If your client has a separate finance or accounts payable team, CC them on the initial invoice email (and all follow-ups). This avoids the invoice getting stuck in one person's inbox.
β BCC yourself
BCC your own email address so you have a sent-record with exact timestamp in your own inbox. Useful if there's ever a dispute about whether you sent the invoice.
β Don't CC irrelevant people
Never CC multiple colleagues at a client company unless you know all of them deal with invoices. It creates confusion about who should respond.
FAQs about invoice emails
Should I send invoices via email or post?
Email is standard for B2B invoicing. Post is rarely used now and slows everything down. Some large enterprises or government clients may request postal invoices for compliance β always ask if you're unsure. Email gives you a timestamp and read receipt capability.
What file format should I attach?
Always send invoices as PDF. PDFs are universally readable, can't be easily edited, and look professional. Never send Word documents (.docx) or spreadsheets β they can be modified and may not display correctly on all devices.
Should I follow up the same day if I don't hear back?
No. Give it at least one business day after sending before assuming it's been missed. Wait until the due date passes before sending your first overdue reminder. Chasing before the due date looks overeager and can irritate clients.
What if my invoice email bounces?
If your email bounces, try a different contact email at the company (accounts@, finance@, info@). If all bounce, call the client directly. A bounced email doesn't extend your payment terms β your invoice is still owed from the original due date.
π Automate your entire invoice email sequence
Chaser sends the right email at the right time β initial invoice, 3 follow-ups, final demand β all automatically, all in your name. Set it up once. Get paid faster.
Start free β